Graves is a very good AD Carry, because of his burst damage. He scales well with most champions and supports, and is one of the most used champions in League of Legends.

I recommend using Flash and Ignite, Flash for escape mechanism, and Ignite for laning phase and utility to use throughout the game. These summoner spells fits in well with support summoner spells such as exhaust.

For the starting item, I recommend Doran's Blade, as it gives you sustain and damage. For boots, I said to buy Berserker's Greaves, as Graves has low attack speed. BloodThirster is the first main damage item that you buy, as its passive gives you extra attack damage and life steal. You buy Phantom Dancer next for critical strikes and attack speed after that. Infinity Edge is recommended after for more attack damage and critical strikes. Last Whisper is bought to finish off your build, with attack damage and armor penetration.

Buckshot has to be the first prioirty, as it is the main source of your poking and burst damage. Quickdraw is learnt when Buckshot and Collateral Damage isn't available, and smokescreen is learnt last in your abilities.

For masteries I recommend 21 points on offensive, and 9 points on defensive. 21 points covers most of the damage output masteries, and 9 points on defensive focuses mostly on health, and armor. These masteries grants him great sustain, especially in the early game laning phase.

As Graves already has damage output from Doran's Blade and Masteries, I recommend to get 'When Level 18' Marks and Seals for better mid game and late game. For Glyphs, I recommend flat Mana Runes as Graves needs lots of mana throughout the game. For Quintessences, I recommend flat attack damage runes for the early game laning phase.

It is essential to farm at the start, but don't play too passive, get some poking going around using buckshot and try for kills with jungler every now and then.
In teamfights, always stay behind the tank and try to put out the most damage possible to all enemies, as you are the main source of damage.

Again, Graves is a very good choice of AD Carry, and if played well, you will be the team carry and lead your team to victory!