At the highest level, find items that let you do what you need to do better.
Since you are trying to play support, and specifically Bard, that will be a good first example. So, what does Bard want to do?
(Note that the order I'm talking about these is not necessarily the order in which you will build them)
- Bard wants to collect chimes for his passive. To do so, he needs to be able to move around the map quickly. Hopefully, this will get you looking at boots. The best boots for roaming the map are: Boots of mobility

- As a support (any support, not just Bard), one of your primary responsibilities is to establish vision control. Trinkets help, but are not sufficient. To get vision control, you will want to aim for a Sightstone
. Also, once you have a Sightstone, the ward limit makes keeping a ward trinket less useful, so you should switch to a Sweeping lens
to deny enemy vision. In the same vein, Vision (aka pink) wards
are an important part of vision control.
- Supports generally want to not get CS, so as to allow the marksman to get more gold. To improve gold income, you should look at the gold income item lines
(you can only get one). I have yet to play Bard, but I would guess that Ancient Coin will be his best pickup since he is not melee and his skills do not lend to being tanky (which would suggest Relic Shield) and he doesn't have a lot of poke (to make Spelltheif's Edge easy to get money from). Also, you should consider the final versions of the items and what they will let you do.
- Bard needs to cast his spells a lot. To do so, look for items with cooldown reduction (up to the 40% cap, of course). The gold income lines pick up some CDR as they get upgraded and many of the other items are natural choices for supports.
- Look at what types of damage the enemy is doing and buy items that will help against that. Frozen Heart
is excellent against marksmen (if you are in range for the aura to apply) and provides CDR and mana as a bonus. Locket of the Iron Solari
provides team-wide magic resist and an active shield (and CDR).
To change directions, let's look at the other common bottom laner, the marksman. What does a marksman want to do?
- Damage
- More Damage
- Tons of Damage
There is some variation based on the kit of the champion, but in general you will see items that increase four stats: Attack Damage, Attack Speed, Critical Chance, and Armor Penetration. These status all stack multiplicatively to enable tons of damage and require the marksman to avoid retaliatory damage via positioning out of harm's way.
- The premiere item here, because its passive is the only way to increase critical damage will still provided two of the four desired stats is Infinity Edge
.
- Common picks ups for for Attack Speed and Critical Chance are Phantom Dancer
and Static Shiv
.
- Moving around the map is still important, so boots are good, and boots that make you attack faster are great, so Berserker's Greaves
.
- Vision is important, and each champion has a limit to the number of simultaneous wards on the map at a time. Upgrade your trinket and buy vision wards. In more coordinated play, the blue trinket is common for the marksmen, but an upgraded yellow is as good or better in solo queue.
- Armor is your enemy, so getting items to reduce its effects is key. Due to its percent armor penetration, the premiere item here is Last Whisper
.
- You will probably need some defense for the inevitable time when you will be attacked. Pick something that fits your situation. Common options for a marksman are Guardian Angel
and Banshee's Veil
.
How to round out a build for these roles and customize for the situation of each game and itemize in the other roles is left as an exercise for the reader.
Remember, find items that let you do what your team needs you to do better.