Welcome guys this is my first (serious) build i wrote on mobafire and its on Master Yi.I wanted to create a build for him cause i wanted to share my way of how do i build him .

[color=green]Pros :[/color]
+ Amazing heal and survivability with your Meditate
+ Superb chaser
+ Great damage
+ One of the best tower destroyers
+ Amazing farming/harassing/carrying capabilities
+ Easy to play and cheap (450 ip)

Cons :[/b

- Squishy early game
- Vulnerable to disables/CC
- Can be shut down easily

Runes

Greater Mark of Magic PenetrationMagic penetration Marks

Greater Seal of Scaling Ability PowerAbility power per lvl Seals

Greater glyphs of forceAbility power per lvl Glyphs

Greater Quintessence of Ability PowerFlat ability power Quintessences

GhostYou will use this to catch up enemies or run away from them and combined with Highlander it gives you a big boost of speed

FlashThis is gonna be very helpful as u can flash so u can land an alpha strike easily or to avoid skillshots etc.

My suggested and used core build is :

Berserker greaves Hextech Gunblade Guinsoo Rageblade Malady Abssyal Scepter Banshees Veil

Instead of berserker greave u can pick Sorcerer's Shoes since it will boost ur damage of Alpha Strike.Also, mercury threads is a very good option if they have a heavy CC team since Master Yi is very fragile to stuns etc.The others boots are kinda useless.

Hextech Gunblade is a very very good item since it gives you lifesteal , damage , ability power , spell vamp and a nice active that slows the enemy .
Guinsoo Rageblade boosts your attack speed , your ability power and your damage and its a very good hybrid item.
Malady will boost your attack speed and your ability power a bit since it gives you a nice anti magic resist tank passive.I''l give you a hint for the malady passive.Try always to land some hits to your opponents and then alpha strike them since you will lower their magic resistance and your alpha strike will hurt more
Abyssal Mask will give you ability power and a nice amount of magic resist.Also will give you a passive that lowers the magic resistance of your opponents for 20
Banshees veil will give a fair amount of health/mana , magic resist and a passive that blocks a skill.