Hello! What a wonderful day! Lets get started. this is my very first build, leave any suggestions BELOW! Thank you.

For what you buy should be obvious. Dorans blade is a good starter, and as soon as you can buy boots of speed and then Berserkers greaves, selling the dorans blade for more money (optional: buy one or two HP pots if you don't want to leave ;) )
Then, Hit a good phantom dancer for a decent attack speed,and critical chance. The last whisper gives you TONS of Armor penetration, use that. Pick up the infinity edge, it will give you a a very decent amount of attack damage and more critical strike, which isn't so important. Alternative: Buy the Recurve bow BEFORE the Infinity edge for some more attack speed, instead of attack damage. More Armor penetration with the black cleaver. Thats about ~11k worth of stuff, if you usually earn more buy a bloodthirster

Not much to say here, max volley as soon as possible, and frost shot. Whenever you can, max the enchanted crystal arrow. Lastly is the unimportant Hawk shot, skill it before frost shot if you're very bad at last hitting minions, and every penny counts.

Flash for escaping, and Clarity for the case that you still have full hp in a battle, but no more mana to fire your ultimate to finish your enemy off, use clarity. Alternative: Take ghost or exhaust instead of clarity for even quicker getting out of situations if your flash is not ready.

Ashes Masteries should be 21/9/0 or 21/0/9 First off, if using exhaust, skill cripple, otherwise skill archmages savy. Alacrity for atk speed,Sunder is needed for Armor pen., and skill something you need for Brute force, max that. Max Lethality and Havoc. For Defense, use Hardiness on max,resistance, and strenght of spirit.

Use Desolation and Alacrity.