Master Yi is a champion of many possibilities. He can be played either AD or AP. When played AD, he can be glass canon, tanky damage dealer or offtank. I think its best to build him as tanky damage dealer. You still have absolutely amazing damage, while having decent health with good MR and Armor.

Keeper of the ancient art of Wuju, Master Yi is a mystical warrior from the isle of Ionia. He descended from one of the few tribes dedicated to the preservation of Wuju, a martial art founded with the principles of absolute spiritual awareness of one's self and one's enemy. When the armies of Noxus invaded Ionia, Master Yi joined in the Ionian defense to fight the craven enemy, bringing his village honor through his unparalleled mastery of the blade. The ensuing battles ravaged the land, but no conflict inflicted as much horror as the day the armies of Noxus closed in on Yi's village. Left undefended, the village became the unfortunate test subject of the latest invention by an up-and-coming chemist, now known as Singed. The remains of the village that Master Yi returned to were so horrific that it remains a festering scar on Ionian history. To this day, no Ionian will ever publicly speak of what occurred.

After the Noxian invasion was contained, Master Yi fell into a deep isolation. For years, he trained morning to night, speaking to no one and refusing offers of consolation by fellow Ionians. The only thing stopping him from madly charging into Noxus battle lines headfirst was his pledge to keep the Wuju style alive. Even though he seethed with impatience, his rage became a tool for sharpening his practice of Wuju, developing stronger and deadlier skills for his eventual vengeance. The only thing that roused him was news of the League's formation, and Noxus's subsequent enrollment in the League. Master Yi now brings his mastery of the blade to the League of Legends with unflinching purpose: to avenge his kinfolk and end the predations of the Noxus once and for all.

Health 444 (+ 86 per Level)
Health Regen 6.75 (+ 0.65 per Level)
Mana 199 (+ 36 per Level)
Mana Regen 6.5 (+ 0.5 per Level)
Attack Damage 55.12 (+ 3.1 per Level)
Armor 16.3 (+ 3.7 per Level)
Magic Resistance 30 (+ 1.25 per Level)
Attack Speed 0.679 (+ 2.8% per Level)
Range 125
Movement speed 330

Double Strike

Master Yi strikes twice every 7th attack.

This passive is a beast when it comes to Melee DPS champions. Because this build is critical damage based, your critical is doubled every seven attacks. Also with your ultimate and items you have a lot of Attack Speed, so these 7 attacks are happen in matter of seconds.

Tips and tricks:
Try to stack your double strike before you gank so you hit double damage with first attack.
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Alpha Strike

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.

An amazing tool for jungling, farming, escaping and catching up. This skill allows you to pass by wolfs and wraiths in matter of 1 or 2 seconds. When maxed deals 300 damage, which is respectable, since you're not building on AP.

Tips and tricks:
There is a picture explanation on how to use Alpha Strike in Gameplay section
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Meditate

Master Yi rejuvinates his body by focus of mind, restoring health and increasing his armor and magic resistance for a short time.

Even thou I leave Meditate for last, its an incredible tool on Master Yi because of his squishiness and vulnerability. This skill is mostly underrated on most players.When at level 5 it heals you for 700 over 5 seconds, and in that time grants 300 Magic Resistance and Armor.

Tips and tricks:
This skill grants you 300 Magic Resistance and Armor. Use it wisely against champions like Karthus when they use requirem.
This tool is amazing when it comes to survivability with low HP. You can trick your enemies into towerdiving you, granting yourself an easy kill.
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Wuju Style


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.

This is pure ownage skill on Master Yi. Because of massive amounts of AD that this skill provides, I first take Phantom Dancer providing Attack Speed and Critical Chance. At level 5 only passive already gives 35 AD. When activated, you get 70 AD boost for 10 seconds.

Tips and tricks:
Since last patch, this skill can be actived when in Alpha Strike form. Activate it while you're in Alpha Strike so your first hit will be affected by bonus.
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Highlander


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.

This skill is epic. This is your chase, escape and kill resource. You have a problem with enemies chasing you? Press R. Your enemies too fast for you? Press R. Not dealing damage fast enough? Press R. For what it offers, it has low cooldown. When maxed it gives 40% Movement Speed and 80% Attack Speed for 12 seconds. If thats not enough, this skill makes you slow immune when active.

Tips and tricks:
If you kill an enemy during Highlander is active, all your cooldowns drop to 0 and you're skills are available again.
Combined with Wuju Style this skill is pure beast dealing damage in fast time frame. Use this in your advantage and backdoor when possible.

Flash

Teleports your champion toward your cursor's location. 265 second cooldown.
Help's you to escape enemies or chase them.

Exhaust

Exhausts target champion, reducing their Movement Speed by 40%, attack damage dealt by 70%, and ability and item damage dealt by 35% for 2.5 seconds. 210 second cooldown.
Make's your enemies to make less damage and slows them down.