Master yi

Yi main here. After playing him a ton in literally every role with pretty much every viable rune/mastery setup I can say that you should be putting 3 points into Q and then maxing E. If you fully max Q it costs an UTTERLY MASSIVE amount of mana to cast (110 fucking mana at rank 5 for a basic ability like lolwut) but 3 points is the perfect middle ground to where the ability still does great damage but doesn't cost too much mana (90)

If you rank Alpha up to lvl 5 too early then you end up having to back WAYY too much because you're constantly OOM from clearing camps since Yi likes to powerfarm. When you're clearing, to maximize your clear speed and not take too much damage, you should be casting E every time it's up unless the camp is almost dead (that way you don't waste its duration) Also ranking E up to level 5 gives you the added ability of being able to effectively duel tanks and juggernauts which is a MASSIVE plus.

(Ability Leveling) TL;DR: Level Q to rank 3, Then max E so you don't constantly go OOM.

In terms of builds, there are 2 main setups, both with strengths and weaknesses. (You should not be building the same items every game. You should be adapting your build based on the enemy team and the state of the game)

The on-hit build ( Bloodrazor > Boots > Rageblade > Botrk > Tank ) is what you'll be building most of the time (since it's tank meta right now) because it's perfect for slaying tanks and squishies alike. It's not NEARLY as downright explosive as the crit build but it's cheaper, more reliable early and results in you being tankier than the crit build. Botrk and Rageblade are interchangable and choosing one before the other will have a big difference on how your early game plays out. Early Rageblade rush puts out more damage at the cost of not having lifesteal. Botrk rush results in you having more survivability (and a handy slow) at the cost of damage. Those 3 items are pretty much all you need to start slaying shit since E True Damage + 3% Max HP + 6% Current HP + Rageblade procs is usually enough to render ANYTHING dead if you hit it enough.

The Crit build ( IE > Boots > Statikk > Phantom > Blood/Hydra > LW / GA Skip full jg item. If you really need the upgraded smite then trade Phantom Dancer for Warrior or Bloodrazor or pay 650 for the smite upgrade and sell it later.) which is a lot more fun imo, is explosive and downright deadly and does MUCH MORE damage than the on-hit build but is more expensive, and not as good at slaying tanks which is why its a lot less reliable in this meta. That said, it's strength lies in the fact that The crit build is why people fear Master Yi. With the crit build you can kill squishies with Alpha + 1 - 3 AA's which gives it very little room for reaction time. Also along with this, Statikk Shiv/Hydra makes Yi a really good splitpusher too which is a good strategy in low elo. However since the Crit build is full glass cannon, you have ZERO tank stats outside of lifesteal which makes it risky to build if you're not really experienced. You blow things up in a second but you also GET blown up in a second.

(Item Builds) TL;DR: On-Hit build if the enemy team has 2 or more tanks or a lot of cc threats. (Slays Tanks / Cheaper / Tankier Endgame / Beginner Friendly) Crit if there's one tank or none or not very much CC. (EXPLOSIVE DAMAGE that nukes whatever it touches / Expensive / Glass Cannon / Great Splitpushing / Requires More Expertise)

Feel free to reply with questions or message me if you need anything else! Anyways, I hope this helped. Have fun, and may Wuju guide your path friend.

Q max always E maxing is a slow slow slow clear compared to Q max which is th most important thing on yi.

there are 2 builds

On hit razor BT + boots

or the hard carry crit build

blue smite into zeal or BT which ever you have the gold for

then into IE and PD

3 points on Q then max E. Also, get a second point in meditate at level 5 or 7 or just when you need it. Level 2 meditate is really good compared to level 1.

As for build, crit vs squichies onhit vs tanks, look them up in guides or something.