FOLLOW THIS BUILD BROTHERS! AND ALLAHU-AKBAR!!!!!
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.

When it comes to marks penetration runes are pretty much first tier. Armor penetration is extremely useful early game. It helps you take down jungle faster and makes your ganks easier. Combined with Armor Penetration Quints, your attacks ignore almost 20 armor, while basic AD carries start with about 15.


9x Greater Seal of Resilience

These are for early game survivability, both in jungle and lane. You start with very low amount of armor and if you go gank against ad carry which can crit you, you'll die before you even touch them. 13 Armor and start will greatly benefit your ganks and your jungling, since monsters do physical damage.


9x Greater Glyph of Shielding

These are also your defense resource. Many people prefer flat magic resistance Glyphs, which are also viable, but I take these because early game bursts aren't your threat. MR/level scales better in late game and helps you survive strong bursts from AP carries.


1x Greater Quintessence of Desolation

Like Armor Penetration Marks these are extremely useful early game. They stack nice with Marks and combined provide you 20 ArP, which means you deal almost true damage to squishies in early game when you gank.


2x Greater Quintessence of fortitude

Many people prefer 3x ArP Quints but I take a pair of these two because that extra 50 health early game is priceless. When you complete your jungle route you have more health which means you could go gank, while you would usually go back. I simply need to take flat health stats at start, otherwise it doesn't feel right.


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LANING RUNES



My basic runes setup is very similar to jungle ones. The only change here is that I take 3x Flat Health Quints instead of Armor Pen Quints. I decided to build that way for extra survivability early game.



15 Armor Penetration || 13 Armor || 24 Magic Resistance at level 18 || 78 Health


9x Greater Mark of Desolation

When it comes to marks penetration runes are pretty much first tier. Armor penetration is extremely useful early game. It helps you take down jungle faster and makes your ganks easier. Combined with Armor Penetration Quints, your attacks ignore almost 20 armor, while basic AD carries start with about 15.


9x Greater Seal of Resilience

These are for early game survivability, both in jungle and lane. You start with very low amount of armor and if you go gank against ad carry which can crit you, you'll die before you even touch them. 13 Armor and start will greatly benefit your ganks and your jungling, since monsters do physical damage.


9x Greater Glyph of Shielding

These are also your defense resource. Many people prefer flat magic resistance Glyphs, which are also viable, but I take these because early game bursts aren't your threat. MR/level scales better in late game and helps you survive strong bursts from AP carries.


3x Greater Quintessence of fortitude

Unlike jungle, when I'm playing lane I take three flat health quints. That makes me more early game tough and helps me be more offensive by dealing damage, yet surviving. I think that 26 health is way more advantage early game that 3 Armor Pen if you're laning.


Items

Jungling Start & Core Jungle Items



Many take Cloth Armor and 5 Health Potion instead of this, but you can read jungling section to learn why I take this over that combo.




Wriggle's Lantern is your core jungling item. This item provides you with everything that you need for jungling. 30 Armor for extra survivability, 23 AD for more damage, 15% lifesteal for lesser need of potions and ofcourse, 20% chance to deal 500 extra damage to monsters/minions which allows you to take buffs and dragons down in matter of seconds.

Mercury's Treads are your boots. I take these because Master Yi is very vulnerable to Crowd Control effects like Stun, Snare, Suppress,..These give you 35% enemy CC effect duration reduction and 25 magic resist to counter early game AP champions. Like all boots except 2, these give you Enchanted Movement 2, which is priority for ganking.

Ninja Tabi are also viable boots for Master Yi. Take these boots if enemies have no real AP threat or if enemy AD dealers are getting fed.

You should take Sight Ward so you can predict enemy jungler movement and protect yourself from counter-jungling and ganks. Plant it near strategic points like Dragon, Blue and Red buff.

Vision Ward is also a viable choice. If you think that enemies have warded your jungle, you can take this item to detect enemy wards. It's a little more expensive, but it may pay off with protecting yourself in jungle.


Laning Start Items




Boots of Speed and Potions is my #1 start. You can escape ganks and you can catch enemies. Because of these you are more vulnerable early game and because of that, I take pretty defensive runes and put points in defense mastery, so you still have same health as you would have started with Doran's item.

Doran's Blade and Doran's Shield are viable aswell. Take Doran's Blade if you want more health and damage early game, and you don't need moving speed. Take Doran's Shield if you are zoned and you need Health regen, health and Armor.

Offensive items





Phantom Dancer provides massive attack speed for your attacks. Also provides critical strike chance which is a good combo with Infinity Edge and 15% movement speed for more mobility.

Infinity Edge provides most AD Damage boost in game. Also has 25% critical strike chance, but what makes this item special, is its passive, which makes your critical strike deal more damage.

The Bloodthirster is your lifesteal item if you are laning. Gives amazing Attack Damage and Lifesteal, but then you need to be careful not to die, because then stacks reset.

Atma's Impaler is a viable item if you intend to build on HP. Gives 2% worth of HP in damage, which about 55 if you have 2700 HP. Also gives critical strike chance, which is good if you're taking Infinity Edge.

Take Stark's Fervor if you have many team buddies that also need Attack Speed, Lifesteal and Health Regen. Pointless to take if you have no other AD dealer.

Last Whisper is kind of desperate item. Not effective if enemy is based on squishies, but its a must if there are champions like Rammus in the battle that have 200 armor.

Defensive items





Frozen Mallet is your chase/defend item. While it grants you small AD boost, its great for chasing with passive slow combined with your ultimate. On top of that, this item grants you 700 health, which is great, since Yi has low HP pool.

Quicksilver Sash is your MR and Anti-CC resource. You get 50 MR which is nice again magic damage dealers and you get a low cooldown active, that is similar to Cleanse.

Combine Banshee's Veil in your build if enemy team is AP based and are mostly casters, yet you don't think there's a need for Quicksilver Sash. You gain passive spell block and good amount of Health, Mana and Magic Resist.

Warmog's Armor is the best item, if you intend to build offtank Master Yi. I personaly prefer Frozen Mallet over this item, but it's still viable due to its huge HP gain.

Guardian Angel should be taken if you find yourself dieing to often and if enemy team is composed both of AP and AD. Its great in some scenarios like: You towerdive, kill your enemy and yet you die. This item revives you with 750Hp, which is enough to get away from tower and survive.


Youmuu's Ghostblade

There has been an epic debate about Youmuu's Ghostblade on Master Yi for a long time. In my build I choose Phantom Dancer over this item. And now lets look at Pros / Cons of taking PD over YG.



Pros
Massive attack speed boost
15% Movement speed
Massive Critical Strike Chance boost
SPACE

Cons
No Armor Penetration
No Cooldown Reduction
No AD boost


So what do we gain and what do we lose if we buy Phantom Dancer over Youmuu's Ghostblade:
+15% Movement Speed
+15% Critical Strike Chance
+55% Attack Speed
-20 Armor Penetration