fr0ggyfr0g and deathalo44 for helping me to test out my build.
VeNaH for pointing out the many improvements available and the many errors. ^^

16-4-11: Changed the mastery to get an extra point in the last skill of Offence and added new choices of starting items. Added more descriptions to Summoner spells. Changed small error in Runes. Credits to VeNaH for the suggestions. Added Changelog.
15-4-11: Created the guide

Pros:
- Good right-click damage
- Has a imba heal
- Fast Movement speed: Can catch almost any hero with appropriate core
- All skills will refresh when you kill a hero
- Easy-to-use

Cons:
- Hard to play well
- Quite squishy
- Useless when stunned/feared/disabled.
- Looks kinda weird with that beehive thing on his head

Utility is overall much more important than offence, add utility first! Perseverance is a must-get since it boosts your meditation! of course, the exp boost is really handy too.
Armor penetration is the best, armor is always good and cooldown reduction helps a lot.

- Master Yi strikes twice every 7th attack.
: This skill is the most important to you. It can burn down an enemy's hp earlier on in game. It can also be used to last hit easily. Great synergy with skills that have on-hit effects like Black Cleaver and Madred's Bloodrazor.

- Master Yi leaps across the battlefield with blinding speed, dealing magic damage to multiple units in his path with a chance to deal bonus magic damage to minions.
Master Yi leaps across the battlefield striking up to 4 enemies, dealing 100/150/200/250/300 (+1 per ability power) magic damage to each enemy with a 20/30/40/50/60% chance to deal 400 bonus magic damage to minions.
Cooldown - 18/16/14/12/10 seconds
Cost - 80/90/100/110/120 Mana
Range - 600
: Your bread-and-butter skill. It has good multi-target damage. This skill has many uses, you can use it to get close to the enemy so that you can land your hits. This skill can also be used to escape by alpha striking a creep. It has great damage for a multi-target skill, since you can clear out the wraiths camp with just one lv4 alpha strike, if you are lucky enough to deal the bonus damage.

IMPORTANT NOTE! When you click on an enemy for Alpha strike, you will end up at the target you clicked on after you finish your alpha strike.

- Master Yi rejuvinates his body by focus of mind, restoring health and increasing his armor and magic resistance for a short time.
Master Yi channels, restoring 140/280/420/560/700 (+1.65 per ability power) health over 5 seconds. While channeling, Master Yi gains 100/150/200/250/300 armor and magic resistance.
Cooldown - 35 seconds
Cost - 70/85/100/115/130 Mana
Range - Self
: Fast heal, Average Mana cost. One of the fastest healing skills in the game, but needs channeling. This can be used to heal after a team battle. Personally if only one enemy is chasing you, you can activate this to stall time so that your allies can get to help you, or you can perform a counterattack after healing. Take this skill earlier on as it is more useful that Wuju style. It can boost great survivability and farming in lane.

- Master Yi becomes skilled in the art of Wuju, passively increasing the power of his physical attacks. Activating Wuju Style doubles the passive bonus damage for a short time, but the passive bonus is temporarily removed after the effect wears off.
Passive: Increases physical damage by 15/20/25/30/35.

Active: Master Yi can activate this ability to double its effectiveness for 10 seconds, but this removes the passive bonus until Wuju Style becomes available again.
Cooldown - 25 seconds
Cost - 40 Mana
Range - Self
: Great Base damage boost for many uses including last hitting and damaging the enemy hero.

- Master Yi moves with unparalleled agility, temporarily increasing Master Yi's movement and attack speeds as well as making him immune to all slowing effects. Additionally, killing a Champion refreshes all of Master Yi's cooldowns.
Increases Master Yi's movement speed by 40% and Attack Speed by 40/60/80%, and he becomes immune to all slowing effects for 6/9/12 seconds. Additionally, killing a champion refreshes all of Master Yi's cooldowns, and scoring an assist reduce the cooldowns by half.
Cooldown - 75 seconds
Cost - 120/120/120 Mana
Range - Self

: Used to chase easily. Fast Cooldown, and the best thing is that the cooldown resets after killing a champion, which means it is readily usable. Can be used to kill or escape ganks, since you cant be slowed while this skill is active. All in all a good ulti.

Skill build:
is very useful earlier on, but you lack the attack speed to utilise it to the maximum potential, while can help you regen after a battle or even in lane. Your heal gets less and less effective throughout the game too, therefore you should max it out early to use it to the maximum potential.


For your skills, you may go for two builds:
OR

Add more points in this instead of if your lane opponent is not very painful. This skill can help you deal more damage and it also makes last hitting easier. If you go for this build, get a to make use of the extra damage for lifesteal.

Recommended by me.
This skill is handy and add it when your lane opponent is harassing you a lot or when you are ganking a lot. It can provide a quick heal. If you are planning to go for this build, is a must-get!

x9 for some chance to evade attacks in sticky situations.
x9 to reduce all your skills' cooldowns, useful since you have 4 active spells.
Greater Mark of Desolation x9 for dealing more damage to tankers, which you have the most problem with.
Greater Quintessence of Desolation x3 for dealing more damage to tankers, which you have the most problem with.(same as above)

You may use other skills, but personally i prefer these skills as they bring out master yi's potential.


This skill can help you to escape sticky situations after rushing tower for kill or when escaping from ganks.


This is a very useful skill. It can be used to teleport toward a lane creep when your teammates are getting ganged, so that you can initiate a counterattack which is vital to your team's victory.


This skill can help you to chase or escape when stunned/feared. As mentioned above, you are useless when disabled with your average-low hp. Can be used with if there are a lot of disables in the other team.

_____________________________________________________________________________________________
These are the other skills explanation:


This Spell is probably unneeded in most cases. You will have your lifesteal and to heal easily.

and
Chasing spells. These are Unneeded. You can already catch your enemy easily with the combo of and .


Used to jungle/last hit. Not needed if you are going to solo mid. You also have to last hit easily. If you want to jungle, refer to another guide: Jungle Master Yi


Not needed, as mentioned, you can catch any hero easily and don't need a finisher.


Can be really good if your team wants to push fast. It's best to have another player get this skill since you have other skills to invest on which are much better.


Not really needed. Get for mana regeneration needs.

*gank: gang kill

Starting items:

for some mana regeneration to use and to harass a grab a quick kill. It also provides you with some extra health to survive. This is useful the whole game as it provides mana for and .


for extra movespeed which can later be upgraded into
Only get this when you are going to a side lane. Boots not needed when you mid, since there is no space for chasing.


You may use this if you want to add more points in instead of


Any amount you need for basic survival.


Then proceed on to rush your first core item : . It synergies well with your ulti, to gain fast movespeed to catch any hero and kill them , even if they have flash.
Get your for the extra attack speed and movement speed
Go on towards for a huge boost in Atk spd and most importantly, movement speed.
Next, You can go on towards a few items(Situational) :
: if you think that you need more damage. This is the best damage boost for this build.
: If there are a few tankers on the other team.
: Handy for your teammates to have extra Attack speed and Lifesteal to survive better. This is the best choice for Lifesteal.
: the best counter against tankers. Buy only when there are a lot of tankers on the other team.
: Good if the team has many disables. Its more useful than Cleanse and has a lower cooldown too.
: I don't buy it normally, since there are other better choices. But it helps greatly in increasing survivability with its great hp boost.
: this can be bought if your team is on the winning side. The extra movement speed at 20 stacks is amazing.

(Teleport in and ping to gank)
1.
2. Right click the enemy
3. turn on , and
4. $$
Note: It's best to gank only after your .
Note 2: You can do without boots for ganking, as long as you have + , you can catch almost anyone in mid-game.

You may take any lane. It's best to solo mid.
Advantages of solo mid:
You have quite low starting hp, even with doran's ring. Going 1v1 is easier as you can catch the enemies in alpha strike easily. Best lane opponents are probably low-hp ranged heroes like ashe and caitlyn.
You have to get to lvl 6 fast in order to gank with ease.
You need to farm in order to be useful in teamfights.
You can down the tower quickly using alpha strike to clear the creeps to push then double striking the tower. repeat the process to easily down the tower earlier on so that you can give a great boost to your allies in terms of gold. You may also kill easily if the tower is down.

How to solo mid:
Start out with .
Harass using (It's the best to wait until there are only 3 creeps and the champion, then alpha strike by clicking on the creep, in order to last hit and to harass the enemy champion at the same time.)
if your health is getting low.
Harassing and Killing:
when necessary, and keep harassing with , until the enemy drops below half hp, then him to get near then right click him and turn on + [+ (if you have it)] to easily kill. You may try to rush tower if you are confident of killing. If you lost hp during the battle, easily use to heal back.