Hi, I'm narsil and i present you build for Master Yi, which I play as long time. I think that this is one at many builds for this champ. Seals for critical damage, because we get items with many critical chance

Standard...
I choose Quintessentials for Armor penetration, marks too, glyphs for AD because we deal more damage in first minutes of game. This runes help us with get many kills and fast win.

Of course, master are ad champ, and we choose only ad masteries, we make stronger us attack damage, and make, that we more often deal critical dameges. Other points we use to increase our defence and speed recall.

To start we buy boots and 3 health potions. Next we buy Berserker Boots, and Vampiric Scepter. Later we buy Zeal, or, if we have many gold, all Phantom Dancer. Next we buy Wriggle Lantern, and Phantom, if we didnt buy it earlier. Later we buy Infinity Edge, The Black Cleaver. If we need, buy something to defence, or if we dont need, we buy next Infinity Edge

I get only this 2 spells, Exhaust and Ignite. First spell are useful if we fight with fast and strong enemy, second we use to killing escaping enemy.