I am a big Master Yi fan and i play him in normal when i feel tired for a serious game. Master Yi is one of the funnest champs to play because of his crazy and amazing damage and the ability to rip apart all the enemies in seconds. Master yi can kill other carries in less than a few hits, and roam around from one end of the map to the other in seconds with his >500 movement speed and more with his ultimate. The whole map is yours when you're playing Master Yi.

There aren't much point in listing out the skills and descriptions since they can be found on various League Of Legends information sites like the "League Of Legends Wiki".

Build No.1 is for ranked plays and advanced players.
Build No.2 is a build for lower level players.

Build No.1 takes some survivability and Madred's Bloodrazor because enemy champions usually have a lot of health, even DPS's like Xin Zhao.

Build No.2 has the best balance between damage, critical strike chance, critical strike damage, attack speed, and lifesteal in order to get the most damage, but without any survivability other than supporting his health with lifesteal.

I made this build to show how to get the most Damage(including Critical Strike) and Lifesteal on a DPS Champion, with the Item Combo: Berserker's Greaves, 2 x Phantom Dancers, 2 x Blood Thirsters, and Infinity Edge.

For lower level or ELO players, it is a great idea to buy full damage based runes as it adds more damage to your fun play with master yi ----

Armor Penetration
Attack Damage
Attack Speed
Critical Strike Chance
Critical Strike Damage


However when getting Critical Strike Chance and Attack Speed runes becareful that you don't have more than 100% Critical Strike Chance or 210% bonus Attack Speed when used with your build because anything more than that will be wasted.

Dont be afraid of being too squishy because you can't die when you have that much Damage and Life Steal from Bloodthirster

For more advanced players and ranked games, i suggest getting Armor seals, Magic Resistance Glyphs, and Health Quintessences. Having a good start will effect your late game, flat runes are always good, but he is late game OP, so level 18 runes are also good.

For Lower level players:
Get as much offence as possible (AD)

For More Advances players:
Utility or Defense are also preferable,
Durability would help him survive more if you are playing a more tanky Master Yi,
Utility: Mana Regeneration, Gold and Experience helps him harass and farm in laning phase

To get the most damage you need to find the balance between Attack Speed and Damage, Damage is made up of Attack Damage(AD) and Critical Strikes, and Critical Strikes are enhanced by Critical Strike Chances and Critical Strike Damage. Phantom Dancers are this build's attack speed item, but it does not only give Attack Speed, but also Damage because it gives Critical Chances, which multiplies with Infinity Edge's Critical Damage to get Critical Strikes. Blood thirsters give the most damage and life steal in the game when stacked up(if you died and lost your stacks, always stack up your blood thirsters by killing minions before fighting again, it gives you 80 more damage and 20% more Life Steal).

Stacking Infinity Edges? This is not as good because a lot of things in this build are wasted:
1) 2 Phantom Dancers give 60% Critical Chance and 3 infinty edges give 75% Critical Chance, that's 135%. 100% means you will Crit every hit, so 35% more Critical Chance will do nothing.
2) Infinity Edge's Unique Passive that gives you 50% crit damage does not stack.

But if we get rid of 2 Infinity Edges all the problems will be solved: not having over 100% Critical Chance, not wasting and stacking their Unique Passives. Now there are spots for 2 blood thirsters which give more damage than Infinity Edges and 50% Life Steal! :)

Stacking Bloodthirsters