Build Guide by Aldriel

To play well as Master Yi you have to combinate Speed to Damage and Life Steal.
At the begining of the match, if you are able to obtain the First Blood and/or solo, you will be able to be the best of the game. For Yi, Mouvement speed is not so important so buy a Dagger to increase your attack speed by 15%. When you reach your 450 gold go back and buy a Vampiric Scepter. Next item to obtain is Malady. Why Malady ? Because you will gain 15% Life Steal and 50% Attack Speed. After that, you must focus on Infinity Edge to gain +80 Attack Damage +20% Critical Strike and the UNIQUE Passive: Critical hits now deal 250% damage instead of 200%. After obtaining Infinity Edge, you will accumulate kills and with all that money, you must buy a Berseker Greaves or Boots of swifteness and Phantom Dancer. At this point, With Malady, Infinity Edge, Berseker Greaves and Phantom Dancer, you will have 115% Attack speed. After that you will need to boost you Ability Points and buy an Hextech Gunblade for +60 Attack Damage +75 Ability Power +15% Life Steal +13% Spell Vamp and its super active: Deals 300 magic damage and slows the target champion by 50% for 3 seconds (700 range). 60 second cooldown. The final item that I recommend you is the BloodThirster because it gives you extra damage up to 40 ( so +100 ) and extra Life Steal ( up to 25 %) so you will be able to own all players :D

The best teammates for Yi is Ashe for her slow and Singed or Blitzcrank for their Grab so if you have one of them in ur team, try to play on the same lane if you wanna get a lots of kills

I hope you enjoy my build. For any questions don't hesitate to ask :)