Choosing runes? I can help you do that better.

Shortly after patch 4.5 (when some runes were reworked), I created a rune efficiency table and uploaded it here. The changes to AD items in patch 4.15 made the efficiency of crit damage runes a little off, so between that correction and the transition to boards, I figured I'd reupload the table here. Note that these are all tier 3 runes. I would just upload the spreadsheet, but apparently boards don't support that anymore, so i guess a screenshot will have to do.

Edit: Here is a link to the spreadsheet: https://docs.google.com/spreadsheets/d/1HS9p4MINutH58DwvGV84tB43ABom9Q9LtSflv-1we9k/edit?usp=sharing

Overall, this chart shows mathematically recommended runes (in green), situational runes (in blue) and poor runes (in red). It uses the gold values of the stats granted by the runes to compare runes of similar type to each other.

Be warned: a rune being gold efficient does NOT, inherently, make it have a stronger impact on the game. You also have to take into consideration what the stat actually does and how well you can make use of that stat.

The idea behind the chart is to help you avoid very low benefit runes shown in red, and help you to use runes shown in green wherever they make sense. Also, don't be fooled by the gold efficiency of energy regen. They may be highly gold efficient according to my formula for conversion of mana gold value to energy gold value (which may or may not be accurate anyway), but that doesn't make them good overall choices.

There is also another way to look at efficiency of stats. The method I used in this table is opportunity-cost; that is, it compares the gold value of what you are getting to the gold value of what you could be getting instead. The alternative method is to compare horizontally. That is, how much armor does an armor mark give compared to an armor seal, glyph or 1/3 of a quint. This can be useful if you're interested in getting a particular stat or combination of stats. If this doesn't make sense to you, don't worry about it too much- just go with what's on the table or what I talk about next and you'll be fine.

Now it's time for some pro tips and tricks:

Marks:

Hybrid Pen: These are good on some mid laners, some supports, and a very few tanks and bruisers. They are good when your primary source of damage is magic damage, but you also deal some physical damage through auto attack harass or spells.

Magic Pen: These are good on mid laners, a few tanks, some supports, and jungle fiddlesticks. They are better than hybrid pen when you have little to no ability to auto attack, and deal little to no physical damage with your skills.

Attack Damage: These give good early game harass, last hit strength, and decent all in potential to AD and/or ranged champions. They are the best and only real option for ADCs, and a good option for junglers, bruisers, tanks, and some supports. AD offers stronger damage in ganks to AD-oriented junglers, particularly ones with skills that scale well with AD. Bruisers and tanks gain better trade potential and better early last hitting from AD marks. Supports gain higher harass potential with auto attacks, and in the case of all-in supports like Leona, some additional damage in an all-in.

Attack Speed: These give very good early game all-ins, particularly in combination with on-hit effects. They grant junglers (even AP ones) the fastest clear time, and tanks and bruisers like Irelia can make great use of them.

Armor Pen: These can be good on AD mid laners, and junglers can choose to take up to 6 of them. Armor pen scales better into late game than attack damage, and works well with high base physical damage skills. 4-6 armor pen marks will give junglers with high base skills, such as Hecarim, more damage in ganks than attack damage. 4 armor pen marks will give 5 armor pen, which is the same amount that lesser wraiths have, meaning it is the largest amount of armor pen that will increase your damage in the jungle to all mosters. 6 armor pen marks will give 7.7 armor pen, granting more damage on ganks but not being quite as efficient in the jungle.

Armor: Armor marks are a bit of an anomaly. If you look at their efficiency, they look very bad (39.5% efficient). However, compare the amount of armor they give to the amount of armor seals give, and you'll get a different story. Considering the higher efficiency of HP seals compared to armor seals, and the lower efficiency of HP marks compared to armor marks, if you goal is simply to have the highest effective physical health at level one possible, it makes sense to take armor marks and health seals. Armor marks can also make sense against certain high physical damage dealers (Fiora) or as Malphite or Rammus. Essentially, they can be an option for some supports, top laners, or junglers under the correct circumstance.

Crit chance: You can take ONE crit chance mark on any champion. I think it's cheesy and would rather have the guaranteed benefits the 1 extra ad/pen/whatever mark would give me, but if you happen to crit on the enemy champion, you can automatically win the trade/lane. Don't take more than 1.

Seals: Health: These are the strongest level 1 defensive seals for an all-in. If you are going to walk up and instantly fight the opponent to the death without backing off, these are the best thing for it. They are useful against all types of damage. Note that level 1 magic resist is higher than level 1 armor, making these a little stronger against magic damage than physical damage.

Armor: These are the next best level 1 defensive seals for an all-in. They are stronger over time than health, as they scale better into late game. Also, they are better for sustain, poke, and trade lanes. They make your health regen and natural health gain per level stronger. Armor seals help against minions, auto attack harass, jungle monsters, and physical damage spells. These are the only real option for pretty much all junglers. When you don't know what seals to take, take flat armor seals.

Health/lvl: These are highly efficient late game and can be very effective when combined with resistance-oriented builds. However, they leave your champion very vulnerable in the early game and are not recommended for melee champions or junglers. It is always a risk to take these seals. They are only advisable if you are confident in your ability to survive lane phase and are capable of not fighting your opponent early.

Armor/lvl: These are also highly efficient late game, and are particularly effective combined with health-oriented builds. Like health/lvl, they leave your champion very vulnerable early game, and should only be take if you are able to avoid early fights.

Mana/5: If you choose these, you have just transformed yourself into the squishiest champion on the rift. Be warned, you are now Anivia, sans egg. Dont take damage. I highly recommend against taking more than 3-4 non-defensive seals, and I really recommend against taking anything but the first four seals talked about. That said, these give a decent amount of early game mana regen for more spam in lane, if you feel that is essential for some reason. If you MUST take mana regen, though, it would likely be wiser to take 3-4 mana regen glyphs instead of these.

Mana/5/lvl: See the warning above. These provide some very early mana regen, and outscale mana/5 by level 7. I don't know why you would feel the need for these as a mid laner when seraphs, rod of ages, grail, and morello exist, and as another role you REALLY need the defensive stats. But whatever, they're efficient and it's your champion so...

Attack speed: Again, see the warning above. That said, these can be entertaining on a couple of champs, they're reasonably efficient, and have enough impact to not make me gag if you choose them.

Glyphs Magic Resist: This is the most common, most general choice for glyphs. Flat MR will give any champion good early game survivability against mages, some tanks, and many supports. Most champions deal at least some amount of magic damage, so taking at least 5 of these is the most standard thing to do. When in doubt, these are the glyphs to take.

Magic Reist/lvl: These are great when your lane opponent deals little to no magic damage, but the enemy team still has quite a bit of it. An example might be laning top against a Renekton (who deals no magic damage until level 6), when the enemy mid laner is Orianna. Again, these can be useful on any champion or role.

Ability Power: These provide a good early game boost to ap-scaling champion's skills. They also improve waveclear, which can be very important. They are a good choice when your lane opponent deals mostly physical damage and you scale well off of AP. Consider taking 4-5 along with 4-5 magic resist glyphs.

Ability Power/lvl: Most of the time, these are less effective than flat ability power. They do grant more AP at higher levels, and will improve waveclear more than flat AP. However, their early game impact is essentially nonexistent. They are an option on some mages and supports.

Magic Pen: Most people don't realize that these runes exist. They are actually incredibly effective when combined with magic pen marks on champions with high base magic damage skills. They also scale very well into late game. However, they do not provide any noticeable improvement to waveclear, and you will miss out on magic resist by taking them.

CDR: These can be effective on manaless champions such as Riven or Rengar. They allow more spam and permit you to reach the cdr cap more easily. They are not recommended on AP champions, who have easy access to CDR through items. Taking 9 of these will grant 7.5% cdr (2 points in cdr masteries for 10%), taking 6 will give 5% ( 4 points in cdr masteries for 10%), taking 3 will give 2.5% (2 points in cdr masteries for 5%). Taking 6 or 3 can allow you to mix in some magic resist.

CDR/lvl: I don't really recommend these, because the cdr comes into effect too late into the game to really be noticeable. They can allow you to reach the cdr cap even more easily than cdr flat runes, though, and again can be effective on champions like Riven and Rengar.

Mana/5: Taking these will grant you a somewhat noticeable increase in mana regen early game. If your champion is particularly spammy with mana issues, I suppose they can be okay. Note that you're missing out on magic resist or ability power, though, so it would be better if you could just manage your mana better...

Mana/5/lvl: Similar to mana/5, except weaker early and stronger late. I don't see the need for them when grail/morello/seraph/roa exist, but they're efficient so if you insist...

Attack speed: Taking 4-5 of these can be an option on ADCs. They will provide a slight bonus to your DPS throughout the game, and if your opponent lane doesn't deal too much magic damage they can be effective.

Mana: If your name is Ryze or Blitzcrank, these can be good.

Armor: Only in very strange circumstances when you know exactly what you're doing.

Quints These are really wide open. Almost all quints are at least okay. Instead of going through all your options, I'll tell you the ones to NOT get.

• Anything per level. Quints tend to be less efficient in the per level category than the flat one, and quints are where you get your biggest early game bonuses. Don't take any per level quints.

• Crit chance/crit damage: Only gangplanks and trolls take this. Wait, what am I saying, aren't they the same thing? YAR HAR HAR!

• CDR: If you need cdr, take cdr glyphs. Quints are for combat stats or something you can't get in marks, seals, or glyphs.

• HP: Trust me on this one: if you want flat HP, take hp seals and armor quints, not the other way around. I've done the math, you'll get more stats doing it my way. The exception is %hp, but that's not efficient for a really long time. You're better off without it.

• Mana and mana regen: Not combat stats for anyone but ryze and blitzcrank. Even they are better off with other things. If you need mana/regen, get an item or, if you insist on it, a few mana regen glyphs.

• Energy and energy/5: Just... no. Please... no.

• Bonus experience and minus time dead: Bonus experience is only good for trolling as/with a Zilean, and you shouldn't be planning on dying, so don't get minus time dead.

All other quints can at least be useful situationally.

Usual Rune Strategies Here I'll list the basic, standard setups everyone can make use of.

Standard ADC, Jungle, and AD assassin: Marks: Ad Seals: Armor Glyphs: MR Quints: AD

Standard Attack Speed ADC: Marks: AD Seals: Armor Glyphs: MR Quints: Attack Speed

My Attack Speed ADC: Marks: AD Seals: 7x AD 2x Armor Glyphs: 4x MR 5x Armor Quints: Attack Speed

Standard Bruiser/Tank: Marks: AD Seals: Armor Glyphs: MR/Lvl Quints: AD

Standard Mid: Marks: Magic Pen Seals: Armor Glyphs: MR Quints: AP

Standard Support: Marks: Hybrid Pen Seals: Armor Glyphs: MR/Lvl Quints: AD

Finally, some notes about the way i calculated the efficiency of some stats that most people do not have an efficiency for. I found the gold value used for crit damage by other people to be much too low, using the gold efficiency of a fully stacked bloodthirster (140.4% efficient) and the other stats granted by infinity edge.

Energy and energy regen are obviously impossible to buy in game(with gold), making it difficult to come up with a gold value for them. However, if we take mana cost per spell over the average mana pool and multiply that value by average mana regen, this number gives us an idea of how much normal spells cost relative to most mana pools and mana regens. We can compare this to the average energy cost per spell over the average energy pool (which is always 200), multiplied by average energy regen (also constant at 50/5). We can set those two equations equal to each other and put both underneath gold value of energy regen or mana regen, and solve out for the gold value of energy regen. This takes into account the different pool size, energy/mana cost of spells, and regen rates of the two different statistics before equating the two gold values, which makes it about as good an estimate of the value of energy regen as is possible.

In calculating the gold value of energy, I used a somewhat different procedure. While regen for both energy and mana allows more rotations of spells, flat mana/energy (generally) is only restrictive in short-term usage of abilities. Because of this, I remove the mana regen and energy regen from the previous equation. Also, instead of using the average cost/spell, I use the average cost/spell rotation.

Spellthief's Edge is used as a basis for the gold value of GP10. Other pages have instead used the time it takes for the gp10 to pay itself off, which is another option. This number, however, is more easily compared to other runes.

Percentage movement speed can be purchased in game, but none of the items giving it is particularly useful for evaluating its gold value. Instead, I multiplied the average base champion movement speed by the percentage movement speed, and that number by the gold value of flat movement speed. Note that purchasing boots or getting other sources of flat movespeed will increase the efficiency of percentage movespeed.

I did not create gold values for percent health, -time dead, or +exp gain. I couldn't settle on any way to make one, so you'll have to judge their value for yourself.

Anyway, I hope this very long post was helpful in your quest to choose the best runes!