Hello, this is my frist LoL Guide. Its about Master Yi in 3v3, which is in my opinion one of the best 3v3 Champs to pick. I want to be honest to you so i am not a pro at all, i started LoL 1 1/2 Months ago, but i read Guides like Crazy. I hope you can see over that fact and read my unbiased.
But instead of waste your time with useless introductional text, i will straight come to the guide.

Master Yi is a very good Character for 3v3. You will not Win every Match but you have a good Winn/Loose Quote AND your K/D will be awesome high. (If you hold on my guide)
Okay but now the Pro and Contra of Master Yi:

Pro
- Awesome Farmer
- Awesome SHREDDER
- Can take out the hole 3v3 team in 10-15 seconds
- You love damage and speed -> You love Yi
- Tower Destroyer (You will have no Probs with them)

Contra
- A little bit Squisy the whole game
- Can be countered with Slows (Slows are your enemys)
- Always hated (Could be a Pro too ;) )

21/9/0.
I think thats clear.
You want to have Attack Damage to get your enemys down and a little bit Defense so your squishyness is reduced.

Most people i think would give you the advise to take Flash. But i wont.
From my experience i can tell you that your so fast with your Ultimate, that you wont need it.

My combination:


Exhaust - So necessary in 3v3, i swear you will love to put your enemys on slow while your are running like HELL on to them and punch them in the nuts. Master Yi will definatly use this spell for your advantage.


Ghost - Good for Hunting Good for flee. Temporary thats your skill whenever your Ultimate isnt avaible and you need to chase somebody or flee with low Hp. Mostly thats the Skill i get very close kills with so its worth to take it.


Also good but in my opinion not the Best:


Flash - Yes i told you not to take it but if your Flash addicted its not a bad spell. But sometimes in the heat of the fight you can definatly forget to use it and place it right so watch out.

Useless:

Okay the items are all designed for you to have Attackdamage and Attackspeed because you want to shreed your enemys. But before you just buy the first item for Berserker's Greaves, start with Dorans Shield. It is wort it because the additional HP will help you get your first kills in the beginning.

First of all Start with Doran's Shield for 475. After you have 770 Gold go to base and Buy Dagger (for 420) and Boots (for 350). Go ahead shreeding until you have around 600 Berserker's Greaves for 150 AND The first part of the Bloodthirster -> Vampiric Scepter for 450.
Your next item is the B.F. Sword for 1650. Then buy the Bloodthirster for 900. Now can easily shreed one or two enemys down. But increasing your Attackspeed you definatly need Phantom Dancer. Go ahead and buy the first parts starting with Zeal for 1195. Okay just go ahead and buy Phantom Dancer. When you have it you will have a great AS and AD statistic and you can go ahead shreeding and Ganking. But if the game follows on you have to buy: Bloodthirster -> Phantom Dancer -> Bloodthirster -> ...

Sell your Doran's Shield only when you need space for more items. In the Early-Mid Game it gives you nice advantage of your HP.

Core

Thats your Core. Simply these two Items but they boost you as hell. Getting those Items fast and you will have no problems to get your kills.

Early Game

Ok first of all start with Alpha Strike it is definitly good for the first little Teamfight in the begining. Wait until one enemy is chasing one of your teammebers and attack him with Q.
Good coordinated you can get first blood or even 2 kills. Try to make a Mate going Up so you and your 3rd member can be Bottom. Bottom is the best place for you to fight because you have the choice to either gank the upper Champ or just stay Bottom and farm. At the Top you have the high risk of beeing ganked from 2 sides. (The Jungle Above you and the Jungle beneath you). At bottom it is just one side. With your Q maxed you can farm very good and damage the enemy without beeing in his range.

Mid Game

This is also important for the early game: Fighting with Yi. When you see an enemy low Hp or beeing alone 1-2 level under you you can definitly attack him like so: Set off your Ulimate (R) and Wuju-Stil (E) and attack the enemy. If he is fleeing away with sort of Ghost or Flash, Chase him by hitting Ghost AND Exhaust AND (This depends on the situation) teleport on him with Alpha Strike (Q). You can definitly get the kill when nobody slows or interupts you. In team fights its the same but a lot easier because most of them will not flee for like 3-5 seconds and you can make a lot of damage. Always remember your Alpha Strike (Q) is very important when the HP of your Enemy is low. Its like a teleport towards him -> You will definitly love it. Okay now something to the towers: When you attack a tower always use Wuju-Stil (E) it gives you a quite strong additional damage and you can shreed the tower very fast. (With Ultimate it is a 10 second thing).


Late Game

Nothing really to say here. Quite the same as above.
Just one thing: Dont forget that your Ultimate gives you an additional boost of Speed so if you are in a WTF situation dont be afraid of use it to flee. You definitly wanna kick your self in the *** when you die and realize that you had your Ultimate Ready ;)

So thats my Guide on Master Yi I hope you like it. I wont take Screenshots to show you a good game. You can Own with pretty much every hero and get a 30 - 0. But with Yi its pretty easy.
So average stats with him in 3v3 are like 7-9 Kills and 0 Deaths. Then the Enemy mostly surrenders. In case where you have one dude who definitly wants to turn a lost game you can get 30+ Kills and 0-2 Deaths very easy.

I hope you can understand my guide because my english is sooo bad i'm sorry.
Try it and Have fun.