I'll bet you just clicked on this because it looked weird. I mean, you saw Cleanse so this has to be either brilliant or stupid. Though I am bad, this build is guaranteed to carry any (reasonable) game. Master Yi was my first real main, and when I got back to him recently I tried out my old build to see how it would stand in the current meta. Needless to say, it still works like a charm, otherwise I wouldn't be writing this. I hope you enjoy reading this guide, and that you will find a place for this build in your games.

Pros

-Great cooldowns
-So easy to pick up a gecko could do it
-Splitpusher
-Can solo Baron when built right *cough* this build *cough*
-Scales into late game
-Doesn't seem to acknowledge enemy armor, just shreds them apart anyways
-Hard to catch or run from, depending on what you need to do

Cons

-Weak early game
-Common ban in low elo
-Shut down very easily by hard CC
-Ganks are weak pre-6, hardly any better post-6, needs a lot of setup tbh
-Carry too hard and you'll be focused the whole game

Smite Smite is essential for all junglers, enough said.

Cleanse Cleanse is my go-to secondary spell if the enemy team has more than 1 reasonable hard cc (a Singed's Fling into Mega Adhesive wouldn't count as one), especially if multiple enemy champions have a hard CC spell. The only two things that can stop a Yi are immediate deletion by a fed mid/ADC, or hard cc (we don't speak of knockups here). Taking Cleanse gives you some comfort knowing something like a Braum's Concussive Blows won't stop you from getting you and your ADC ahead.

Ignite Ignite, it's extra true damage that helps secure early kills and is kinda useless in the late game, since no enemy will last more than 3 seconds near you, if they're lucky.

Teleport Teleport is the spell I would take as a secondary if the enemy team doesn't meet my Cleanse standards. You have global pressure and become even more of a splitpushing monster than you already are. Also useful for getting to Dragon and Baron's pits quickly, cutting people off, etc.

Flash Flash is what most will take second and I get why: wall hopping, clutching a kill and you forgot to click the dang lantern, gap closer, etc. This is the recommended secondary spell for inexperienced Yi players.

Double Strike The first spell we'll look at is Double Strike, your passive. Every 4th auto strikes twice, the second dealing 50% damage. This synergizes well with devourer, which is one of the reasons we'll be building it.

Alpha Strike Alpha Strike is a very important spell in multiple ways. In fact, it is the most important spell of your kit (maybe Highlander but you'll build enough attack speed to not really NEED it, plus Youmuu's Ghostblade gets you in range to close the gap). Alpha Strike is a point-and-click spell that hits up to 4 targets while making you invulnerable. It deals 25 (+100% of your AD) in physical damage, scaling 35 per point put into it. This spell also deals bonus damage to minions and monsters and can crit for 60% of your AD in physical damage. Alpha Strike's CD is lowered by 1 second per AA. Aside from being a gap closer, this spell is useful for juking skillshots, like Morgana and Lux bindings. When you pull these off you also save your Cleanse for more dangerous CC, such as a Malzahar Nether Grasp. This ability will be maxed first.

Meditate Meditate is the only reason you're useful early. This is your sustain spell that heals you over 4 seconds for 30 HP per second, scaling 20 per second per point put into it plus 15% of your AP. This healing is increased by 1% for every 1% of health you're missing and gives you 50% reduced damage done to you while channeling, scaling +5% per point put into it. This spell is used in high elo as an early AA resetter, but the long CD means you must be sure you can escape the fight alive. This spell will be maxed last.

Wuju Style Wuju Style is this glorious spell that gives you 10% bonus AD passively and 10 (+10% of AD) true damage when active, scaling 5 (+2.5% bonus AD) per point put in. The passive AD of this spell is lost while it's on CD, but that doesn't matter since you'll have already killed everyone you needed to by the time the active is over. This ability will be maxed second.

Highlander Highlander, or the "Sanic Panic" as it has unfortunately gotten the nickname over here, is pretty simple: it passively reduces the CD's of your basic abilities by 70% when you kill or help kill someone, and when active it gives 25% movespeed and 30% attack speed, scaling 10% movespeed and 25% attack speed for point put into it. You also gain immunity to slows while Highlander is active and can extend the duration of it for 4 seconds per each champion kill or assist you get while it's active. There isn't much to say about this spell, it keeps you on the enemy's tail (with the help of Cleanse in some situations) and helps you cut them down faster. You put a point into this whenever you can.

Runes Reforged have been an ***load of fun to try out, and as a fighter/assassin main I have spent too much time learning the intricacies of the Precision and Domination trees. Most people would assume Yi goes Lethal Tempo because it severely buffs his attack speed in teamfights, however Press The Attack covers your weakness in early skirmishes against the enemy jungler (especially now that J4 is meta again). From there, we take Triumph since your damage output will almost guarantee you get the kills you participate in and that means a slow but major gold increase over the course of early and mid-game. After Triumph, move down the line into Legend: Alacrity for the obvious reason of more attack speed. To finish off the Precision tree, take Cut Down so you can shred that frontline all the harder for your carries to reach theirs. Moving over to Domination, the two runes to select are Sudden Impact and Relentless Hunter. Sudden Impact causes your first auto after you Alpha Strike to turn into a nuke that can potentially oneshot an ADC. As for Relentless Hunter, Yi's main attraction is the speed of his ult, letting him reach targets trying to retreat mid-teamfight, and this rune serves to buff that chase potential by providing out-of-combat movespeed to reach teamfights easier or lock down a pick your team started, yet let get away by some dumb escape mechanic like a Blasting Cone.

The path I prefer to go for my first clear is Blue Buff into Gromp, followed by Wolves, Red Buff, then Raptors or Krugs in either order (Note: Wolves are very risky, sometimes within one AA of death. Have your pinkie ready on Alpha Strike). Sometimes if I come out of my Blue side clear a bit worse than usual I'll pause and take a Scuttlecrab, and I always take the Red side Scuttlecrab after I clear that side, since you should smite the Krugs over Red Buff. You should only have used two potions by the end of your first clear usually, but it can be one if your leash is perfect or all three if you had an early gank or jungler encounter/counterjungling.

Now remember, you are a Farm Jungler, meaning you will gank less frequently than other junglers. Ganking will likely happen when you have 2 or less camps to take or if a lane is/will soon feed. Yi is also a post-6 ganker, so you should make it clear to your laners that if they're having a hard time farming or trading that they need to play defensively (you'd be surprised how many need you to walk them through it). There is an exception to this ganking rule where the enemy laner keeps leaving themselves open to consecutive ganks that can get you and that ally lane ahead. Capitalize on these opportunities whenever you can.

It's highly encouraged to take Rift Herald as soon as you can and push out a solo lane while focusing on getting bot lane ahead, so try and rally top or mid for him when you finish a gank for them, or if the solo lanes are already winning so hard they can leave long enough to grab Herald without major consequence. We know how important dragons are, and moreso for you since your clear times once you finish your jungle item leave you with nothing else to do. The same conditions for taking Rift Herald apply to Dragon, but with bot lane (and vision is more important, so always take a Scuttlecrab at the very least prior to starting a Dragon). Scuttlecrabs are subtle crabs and can harshen gank potential
oft he enemy jungler, which makes them a great camp to keep on top of timers for to the level of your buffs, but the amount of time this takes can be inefficient, so don't always go for it.

The latest you should sate on any decent game is 21:00-21:30, and the earliest is typically around 17:00-18:00

Playing As

-Look around before you Q, you might end it in the middle of some hard CC or some unholy burst
-Use Meditate in early fights as an AA reset

Playing Against

-Target him early, the longer it takes for him to get his items the better your odds of winning (even the worst Yi can carry once they hit full build)
-Play a heavy counterjungling champion such as Shaco or Lee Sin if you can, you'll keep him from hitting full build while also getting kills and hopefully tilting him
-Play hard CC champions, especially knockup champions. A Yi's only nightmare is hard CC, and knockups can't be cleansed or mercurial'd

This is nowhere near complete and I'll be sure to update it every so often so stay tuned, folks!