Hey guys! im kYSMIG and im here to tell you how i pubstomp as Yi :D
Hes really fun to play with if your having a bad streak of deaths and that stuff since with this build lets just say they will be naked :)

Pros-
-Great damage output, even at lvl 1
-Very versatile
-Awesome mobility
-Awesome ulti :D (immune to slows pretty fun bro)
Cons-
-Easly shut down, with a stun or blind he mostly dies if the blinded person has some damage
-Low hp pool
-Quite squishy early on
-If ulti is on cd you have to play carefully

These runes help yi alot early game.

REDS:
Armor Pen - For me its every AD choice for reds
YELLOWS:
MP5 - I like mp5 but u can also go with mp5/level
HP/level - If you dont like spamming skills you can go with hp/level since it helps you increase your low hp pool
BLUE:
CDR/level - These runes offer the best cdr out of the flat cdr ones.
QUINTESSENCES:
These are personal preference i like having armor pen, 31 armor pen at lvl 1 can pretty much kill a squishy(il explain later)

Standard 21/0/9 getting more armor pen/magic pen and giving some more damage.

Ghost enhances your escaping/chasing abilities. pretty standard
Exhaust well i got the point in reducing magic resist and armor so it gives you even more armor pen and magic pen early on, at lvl 2 you have a sure kill if they dont have flash or ur teammate has a stun.

At lvl 1 your gonna have 1 point in wuju, u should have around 80 ad i think, simply farm some creeps till you get your double strike.
Once you got that save it and let them push.
Once they are pretty far past river tell your teammate to attack.
Pop ghost get to him - exhaust - wuju style - auto attack - alpha strike (if your lvl2)
he should be dead or pretty low, always remember to go for the one with the lowest armor

Well hope you enjoyed the guide, please test it out and give me some suggestions on what i should improve :D thank you