Master Yi was the first champion I used and has been my favorite the whole time I've played LoL. Once you know how to use him every game you play you do really well. I get 20+ kills a game, win or lose.

This is my first build so sorry if it's looks like **** haha :p

For my runes I just get straight up armor pen and crit damage, just more damage. What more would you want? :)

I max out Alpha Strike first to make farming and harassing easy. Then get Wuju Style for the extra damage. Get Highlander whenever you can. I barley ever use Meditate I just find it useless in this build.

It's so easy to farm minions/creeps with his Q Alpha Strike and E Wuju Style.
Chasing down enemy champions with you Ultimate, R Highlander, it's never been easier. Nothing slows you down.
Almost every time I fight an enemy champion I use Wuju Style and Highlander just because of the movement speed,attack speed and increased damage. I finish them off and the cd's are gone.

For summoner Spells I go Exhaust just to slow down enemy champions and help get early game kills, and Ignite just to help off that last bit of HP they may have.

By late game you should be running around the map 3 hitting every champion, taking down turrets in seconds and winning the game :) Hope this helps you. Thanks :)