When you build Infinity Edge and Trinity Force you will get extreme damage when you are in fight because Trinity will gave you 200 percent of damage and Infinity will gave you big crit.

Berserker's Graves will gave you some Attack speed + movement with alacrity enchantment, Statik will bigger amount of critical damage.

Bloodthirster will keep you alive because of big Life Steal and Phantom Dancer for movement, critic chance and attack speed

When you have full build, with runes and masteries, your critical will do more then 1200 dmg in one single hit without Trinity Force. So If you have trinity you can get more then 2000 dmg in one hit. That's good huh?