i recomend ghost ignite or exhaust.

In the begining first you select alpha srike as ur first ability, the first item u buy is vamperic scepter all you pretty much gonna do is harras with yi with alpha strike wat i usually do i click it on the minion closest to the enemy champion. Your gonna be farming in the begining and you shouldnt have worries about health because of life steal. Your not gonna strt getting kills and strt dominating until you hav your ulti. The trick to yi is u have activate both wuju style and highlander when ur fighting enemy and if there runing away use ur aplpha strike to teleport to them. I recomend that u strt ganking once you have ulti and you have killed your the enemies in your lane.

You should be now fed so team fights should be starting do not intiate first if have a tank and always go for the weaker ones if u get a kill all of ur abilities will not be on cool down.You should know if ulti is on cooldown you could also use yummus as ur ulti also. If u rlly want to attack amazingly fast activate ulti and yummus at the same time. ( careful for any tryns or kayle there ultis will pisss u off when fighting)

U should hav a almost full build and rember to have ur stacks for blood thrister just farm minions and jungle if your the carry get the buffs and baron as soon as u can by now u should attack crazy fast and life steal so much it makes the other team get so mad. when pushing u can solo a turret or in hibitor or nexus by yourself because of ur ulti and wuju style
u could push by yourself or do it alone if your team is defending. Master is really someone you can call a game changer. This is my first build hope u like it.