at the start go red side due to being able to kill bramble much faster than blue buff due to negative armor. next go krugs then skuttle for lv3 then look for a gank. if you cant you can either vertical jungle or do a full clear.
this determines the pace of the game farming is better for slowing a game down and ganking will get lanes ahead but leave other lanes open for counter gank
also by 5 minutes solo drake yi's w will negate dragon damage if your heath is too low then keep farming and ganking.

the mid game is a nightmare especially in plat. most laners either dont know what to do with a lead or throw by being to confident, Vayne mains im looking at you. but you can either go for herald or you can split push a side lane. (note) yi has the strongest two item power spike in the game with blood-razor rage blade as it will take probably 3 people to kill you.

first tip go baron. next shove mid or another lane as a team. next fighting. first off unless you are full build and they have no hard cc dont engage let the enemy waste cd for your team to engage or disengage then reengage any person or team with half a brain cell will focus you. like i said yi thrives in skirmishes and as a clean upper so dont go in with q and expect a penta kill this isnt 2016 with ap yi. next your goal should be focus their back line specifically the support or mage. adc's might be a nice pick but unless you can actually one shot them their support and mage with tag team wwe you into the fountain. with out any backup disengage an adc is a sitting duck that has a sniper rifle,crossbow,axe,or a minigun. the front line wont be able to deal with you fast enough being usually tanks,bruisers,fighters. unless they are a fed jax your fine to ignore them until the carry's are dead. next shove a single lane as a team and end