Msster Yi is a carry, he is very item dependent like most other carries and needs a lot of farm to stay in the game. The point of this build is to eliminate his weaknesses and maximize his strengths. This build will help you if you have any difficulties in farming and laning with Master Yi, which in result not make you a good carry.
Master Yi specializes in killing single targets, his attack speed and attack damage allow him to do so, but his weakness is getting involved in team fights he has no ability to allow him to contribute into team fights & ganks, which most of the team during that situation, he mostly kill steals and gives all his allies assists instead, which could probably result in your team raging at you, but this build will help you not get raged by your friends and at the same time not get killed by your enemies.

This rune build mostly focuses on attack speed, this is to activate your first passive (double strike) as much as possible, this rune build can be altered to make all the runes give you bonus attack speed,but altering it to deal attack damage, I would not strongly recommend, but is still a viable option.

This skill tree is made to keep you alive will being able to last-hit in ganks, but if there were more attack speed related boxes in the current skill tree, I would probably go for those instead, but too bad there aren't. You could also get good hands in the utility tree maxed out too which is a great idea.

If you look at the item build, you would probably ask me: "why are there two phantom dancers?" well the answer is simple, the phantom dancer is probably the item thats fits with Master Yi, the attack speed allows him to activate his 1st passive (double strike) constantly (with 2 phantom dancers, the attack speed will be increased by 110%, which is crazy attack speed for Master Yi, the extra movement speed will allow you to chase and hit enemies, and the critical strike, well, there isn't really much to talk about that, since it helps you in an obvious way.
The frozen mallet, is to slow and hit & kill enemies before they reach their turret and activate their recall, but during the end game and most importantly, if you are winning, will stop the enemy from reaching their spawning pool, whilst you are killing them in their base. The extra health will allow you to survive ganks and ambushes. another item you can probably replace Frozen mallet with is Black Cleaver, it gives you great attack speed and damage, but makes you weaker and doesn't give you alot of HP (actually it doesn't give you any HP at all.) I would only recommend this item if you're planning to gank the whole game and charge right at the enemy base or if you think you can handle the game without getting many deaths.
Infinity Edge, there really isn't much to talk about it, it just goes with the two phantom dancers, end of story.
BLoodthirster, helps you survive the game with alot of lifesteal and bonus attack damage, you can replace it with Youmuu's Ghostblade to make your crit go up to 100% chance and make your Infinity Edge really shine, it also helps you chase down enemies ( which I think I've been talking too much about in this build so I decided to go for a more survivable approach instead.)

The skill sequence, you really should get your third skill (Wuju Style) maxed out 1st, it will give you 35 bonus damage passively at the max level and will give you :D70:D BONUS DAMAGE ACTIVELY , the meditate at level 8 is to help you with laning or farming in case you get ambushed and you really need to heal. your next priority after Wuju Style is maxed out, is to get Alpha Strike maxed out, it really helps with last hitting enemies from far away (NOTE: the enemy you click on with Alpha strike will get hit last, which in result, the enemy you land on after using Alpha Strike, so make sure you use Alpha strike on the enemy you want to kill so you can chase them down easily and catch up with your ulti).

During the early game, while in laning, you should just stay back from the creeps if you see and melee heroes attacking the melee creeps, this is because, almost every other melee hero has a ranged ability, but you don't, such as stuns and slows. You should probably get a ranged hero to kill the creeps for you or a tank, and Alpha Strike the creep you want to kill (DO NOT TARGET THIS AT AN ENEMY CHAMPION IN THE EARLY GAME, UNLESS YOU'RE GOING TO KILL THEM, WHILE THEY ARE NOT NEXT TO THEIR TOWER, BECAUSE DOING THIS WILL GET YOU KILLED AND PROBABLY GIVE OUT FIRST BLOOD OR FORCE YOU TO GO BACK TO THE RESPAWN POOL.).

PROS

He can deal a lot of damage
Great Carry
Easy to master
Killing an enemy champ with your ulti will reset all cooldowns (including you ulti, allowing you to spam it as much as you like, until you get a pentakill :D)
Good at single target killing or ambushes
Ulti has short cooldown, in case you don't get to kill the enemy champion running away like a fried chicken.
Alot of escape mechanisms (kind of.(you can use alpha strike on an enemy minion in front of you to teleport to them when you're running away.))
Has more Pros than Cons

CONS

Bad in team fights
Can die easily when stunned of slowed
Hard to run away when ganked(unless you have a tank willing to die for you.).
Enemy you click on might run to tower, so when you finish you Alpha Strike, you'll end up next to a tower, which has a 99.99% chance of killing you.
Really squishy and cute.
Has 7 lenses because of terrible eyesight.