Hey I'm liquidkoda but my mates call me liquid because it is shorter.
This Guide can help you to deal much amount of damage and survive longer in teamfights because of the lifesteal.

You guys are probably asking why ?
Yeah that is a godd question but the Answer is simple: It is OP on Yi because of all the lifesteal.

Well the combined with can heal u full life with 5 AA.
If u are low on health and a team fight is starting u can still go in because u will heal with your first Alpha Strike toward half or even full life.

Level 1

You should usually start at the blue buff so u can do Gromps and Wolf to archive Level 3 fast.
After u hit Level 3 go use ur Control Ward in the Top/Bot River Brush and get the Rift Scuttler. After u get the first Rift Scuttler u can do your Red Buff Raptors and Krugs to get your jungle full cleaned and hit Level 4

Level 4

With level 4 u aren't able to chase a enemy because u dont have yet Highlander and u shouldnt waste your flash for that.
When u are starting a fight dont use ur E Wuju Style first because u usually use ur Q Alpha Strike first and after that u use ur E Wuju Style to deal extra more damage.

Why not E Wuju Style first and Q Alpha Strike after that?

Your E Wuju Style is active for 5 seconds and when u use the Q Alpha Strike instantly after that to reach your Enemy it doesn't deal extra damage from the E Wuju Style

what to buy first?

You should get as first Item to already get a little bit more Atackspeed and deal more damage to minions and Monsters.

should I start ganging?

Yes but only if u are 75% sure u get that free kill and don't int.
Why 75% sure? because in a gang not only u are able to get a kill your teammates too so if u die and ur team get 2 kills and u 2 assist it is still a win situation for you.

Level 6+

Start ganging more often but never forget to farm so u can afford items to be a 1v9 Carry in mid/late game