So this build its based on i know about this champ. I am not the best but i think i can give you a good build for play and get free Elo, with this build i put my account at PLAT V (at the moment) and my smurf at Gold.

The only Ranks i test this build its at Bronze, Silver, Gold, Plat and Diamond.

ITS A RISK BUILD. If you dont know how to play correctly with Master Yi.

Pros :
Easy vs team´s with less CC
Can easy 1 SHOT, Carry or ADC.
Good vs Tanks with less CC !
Good LifeSteal
Good CDR (30%)
Good Dmg ~300
Good Crit´s (~50%)
COMPLETE CHAMPION

Cons :
Can get rekt by CC Teams
You need to be fast for kill 1 in Team Fight

http://imgur.com/a/e7Rop

This build its created by me and i love this build.

Scores in my smurf account » http://prntscr.com/cre2km / http://prntscr.com/cre2x6

Scores in my main account » http://prntscr.com/cre352

Remember Master Yi its a Farm Champ you only need farm to stay STRONG. If you gank try to gank lanes with enemy less HP or your ally have a good CC.
( I recommend to don´t gank before lvl 6 )

STAY GOOD AND WP FREE ELO !
If you think anything is wrong or i need update tell me in the comments.

If you guys like this build pls UP and i will update this build and this guide every Patch !