Hi guys this is my first try at guide making or discussing 1 of my favorite heroes in the game at the moment. I hope my guide on YI will leave you with the satisfaction that I find every time I play the character. I play YI for crit dmg due to his outrageous ability to chase you down and constant ability use for landing 1 kill.

I prefer crit dmg over armor pen or attack speed. Many will disagree towards the rune choices but I feel that with the amount of crit dmg increase it will make up for it with more kills per game and leave you opponents stunned on how fast you dispatched them.
Each rune of furor for an overall gain of 51.05%( don't forget about the mastery bonus of 10%) crit dmg increase (talk about landing a 1 hit KO for Fblood) and since he has ghost walk and his ulti no player is outside your range of running down. The cons to all crit dmg is you lack jungling runes if you prefer to start the game as a jungler over a solo lane.

With 22/0/8 build you have all the important damage masteries as well as the improved ghost and increased exp gain to get an edge over your laneing opponents. Another build instead of the ghost is the cripple with the point from the savvy into imp cripple and the ghost into the good hands for 3.33%.I would not suggest going for the dodge in the defensive tree to combo with ninja tabi because YOU ARE NOT A TANK.

Since I favor crit dmg you will want a high base dmg and life steal. Try for the berserker boots to start off with and 1-2 health pots depending on how offensive you play and 1-2 mana pots if you like to spam your alpha strike early game for those creep kills. After the starting items if you are good at living and either ksing or soloing the heroes you should aim for bloodthirster so you have time to build up the gains before it really comes into play at mid-game or late(having +40 dmg and 10% LS is a huge boost and worth the gold) and since you lose the bonuses on death be map aware to avoid being lured or ganked and having to regain your stacks. With bloodthirster you should have no problem staying alive from creeps and start making the gold for the infinite edge( you ain't going to destroy without it) and because it is rather expensive keep in mind of the reward for getting the item. After the infinite edge the next items should be chosen due to what you are facing( like if they have a jax get sword of the divine) if they have a tryn whose hitting a tad to hard thornmail is a great way to counter him while using meditate because we all know everyone likes to hit the meditating Yi. I favor the black cleaver before any survival items because you shouldn't be getting bursted down or focuses as quickly due to your insane ability to get in and get out with ulti and ghost walk.

I am unable to get the skill sequence to show for some reason while I'm making this guide so Ill have to improvise.
Alpha strike:1,4,8,10,12
Meditate:13,14,15,17,18
Wuju style:2,3,5,7,9
Highlander:6,11,16
Ill use the numbers 1-18 to show what lvls for the skill.
Now some people might go for alpha strike because of easier harassment/creep kills but wuju style helps your last hitting skill with the passive increased damage.

Because I prefer ghost over cripple I have it improved now either 1 is good I just feel like ghost is more utility in case you have to run from 1 place to another very fast without wasting your ulti.
I would not advise getting cleanse,heal,revive(even though its fun in pubs)Fortify,and all the other spells that do not relate to your guy stomping the opponents. Now those that go jungle Yi might want the smite for the nice damage to creeps but since I do not jungle on him I do not choose it.

With all that being said let me give you a break down in case you haven't the time to look over my first guide. Yi being 1 of the hardest characters to get away from and being full crit based will devastate in 3v3 or 5v5 once you obtain 1-2 items. Focus on squishy targets over tank at first until you hit tanks as hard as squishes( like heimerdinger) and having the ability to get insta refreshed cds per kill makes him one of the few heroes who can go on a chain of killing without worrying about making a get away. I hope you to see more crit dmg Yis in the game to prove how successful crit is in this game.