Introduction
Graves has everything an AD should have and more. He combines many of the other AD's mechanics into one overwhelming entity. His Q is like MF/Ashe/Cait Q combined, his E is like Vayne tumble plus Tristana steroids, his ultimate is MF and Trist's ultimates combined. All of these multi-mechanic abilities allows room for his third ability, Smoke Screen, to be completely unique and game breaking.
Item Build
Openers:

is necessary if you're laning with a non-sustain support such as Blitz, Leona or Janna. Boot3x has become extremely popular recently due to it's high mobility, which opens up a lot of defensive/aggressive options in the laning phase. It's honestly a breath of fresh air compared to the stagnant/farming Dorans v Dorans matchup.
Pro: More skill based, can out-play enemies that run Dorans.
Con: Can die very easily to level 2 jungle ganks. You spend 105G on pots.
Doran's is still good as hell, if you have a sustain support, then be my guest. Dorans still offer great pushing/trading potential, also easier last hitting, which is always good.
Pro: Very tanky vs ganks, can push very fast, can trade hit for hit.
Con: Not very mobile, can only really capitalize on "mistakes" instead of out playing.
First trip back/Early game goals(Recommended 1200G~ if Dorans first, 1300G~ if Boots first):




Try and get B.F Sword as soon as possible, skip unnecessary Doran's Blades, since it will get you your Blood Thirster and late-game so much quicker.
Mid game goals:
then 
Since Graves gains so many defensive stats from his passive, I found buying strictly offensive items better for his damage, while relying on the lifesteal for defense.
Having BT, PD and IE with 2 Dorans as opposed to QSS or GA at this point makes you do significantly more damage with similar sustainability in fights.
End game build: 





Optimal AD Carry end game.
Counters
There really isn't any hard counters to Graves but these champions will give you a hard time:
Ryze/Cassio - Short ranged sustained casters are rough on all low range AD's
Kog'Maw - It's really difficult for Graves to deal with a late-game Kog'Maw due to the range.
Caitlyn - Lane harassment
Maokai - Reduces the damage of Grave's AoE significantly.
Masteries
Meditation is HUGE for Graves, since I've always ran dry on mana in long drawn out team fights. Meditation also makes it possible to spam Buckshot/Smoke Bomb to clear minion waves in the laning phase.
Runes
Flat AD red - These are very nice for last hitting (also better due to 3%Life steal and 10% ARP Masteries)
Armor Yellow - Allows you to win exchanges
MR Blues - Allows you to win exchanges
AD Quint - Same as red
Summoner Spells


Explanation:
Flash: Absolutely necessary tool to make plays and manage situations.
Heal: Allows you win exchanges. (Wins lanes)
Ignite: Also very good for Graves, esp paired up with a strong laner such as Sona.
Skills
Passive: True Grit
Graves gains 1 / 2 / 3 / 4 bonus Armor and Magic Resist every second he remains in combat (stacks up to 10 times).
Graves is treated as in combat if he has dealt or taken damage in the last 4 seconds.
Explanation:
Insanely powerful passive. Try and keep it up at 10 stacks during the laning phase, especially before you engage in a skirmish. 10Armor/MR at level 1 is like having another set of Flat Armor/MR runes. 40Armor/MR is like having a Chain vest and Negatron Cloak. This passive is simply amazing, and makes 1v1'ing Graves very difficult.
Tip: You're extremely potent duelist, try and force 1v1's.
Q: Buckshot
Graves shoots three bullets in a cone, each dealing 60 / 105 / 150 / 195 / 240 (+80% of attack damage) physical damage to all enemies in their path.
Enemies hit with multiple bullets take 35% damage from each additional bullet.
Cooldown 12/11/10/9/8 seconds
Cost 60/75/70/75/80 mana
Range 750
Explanation:
Buckshot is superior to Ashe Q, it hits all targets in the cone and does significantly more damage.
Buckshot is superior to MF Q, it's AoE.
Buckshot is superior to Cait Q, it has no cast time and does more damage.
Granted that Ashe's Q slows, MF's Q has a longer range(possibly) single target, and Cait Q also has a longer range. Buckshot is still as a whole much stronger than the others.
Tip: Landing a close-range Buckshot is harder than it seems, make sure to aim very well if the target is extremely close to you, since a close-range Buckshot and swing the tides of battle.
W: Smoke Screen
Graves fires a smoke canister dealing 60 / 110 / 160 / 210 / 260 (+60% of ability power) magic damage on impact and creating a smoke cloud at the location that lasts (5) seconds. Enemies inside the cloud have their sight radius reduced and are slowed by 15 / 20 / 25 / 30 / 35 % while they remain in the cloud.
Cooldown 20/19/18/17/16 seconds
Cost 70/75/80/85/90 mana
Range 300
Explanation:
Smokescreen is extremely unique of an ability. I will cover some of the uses that I found after the few games I played with Graves.
Extremely strong dueling ability, cast on enemy directly.
Can block off a ramp/chokepoint.
Can be used to bait: denying vision when your jungle comes within range.
Very powerful vs Pantheon/TF ganks.
35% AoE slow is good by itself, can be used simply to catch up while chasing.
E: Quickdraw
Graves dashes forward gaining 40 / 50 / 60 / 70 / 80 % increased Attack Speed for 4 seconds.
Each of his basic attacks lowers the cooldown of Quickdraw by 1 second.
Cooldown 22/20/18/16/14 seconds
Cost 50/50/50/50/50 mana
Explanation:
Quickdraw, much like Buckshot, is a combination of other AD's abilities. Tristana steroids and Vayne tumble combined, but stronger than both as a whole.
Buckshot can pass through most small ledges, has an insanely low CD (supposing that you're auto attacking). Try and JOIN the fight with Quickdraw so you can start chipping away at the CD, do NOT initiate with it.
R: Collateral Damage
Graves fires off an explosive shell dealing 250 / 375 / 500 (+150% of attack damage) physical damage to the first enemy champion hit. After hitting a champion or reaching the end of its range, Collateral Damage deals 150 / 275 / 400 (+120% of attack damage) physical damage in a cone behind the target.
Cooldown 80/70/60 seconds
Cost 100 mana
Range 700
Explanation:
Great instant ranged DMG AoE ultimate. Solid.
It's essentially MF ultimate, except insant... Fantastic for teamfights, also great for dueling.
Nothing much to say about the ultimate... Land it, things die.
Skill Order
Priority: R - Q - 2 Levels of W - E - W
Ultimate whenever - obvious.
Buckshot first - obvious.
2 Levels of W so you can clear the ranged wave with Q-W combo.
I like Quickdraw second because it scales on itself. Lowering the cooldown on Quickdraw lowers the cooldown of Quickdraw, very much like Riven ultimate, where AD scales off AD... Quickdraw's CD scales off CD.
W last because it is very powerful even at level 1.
Early Game
Priority: R - Q - 2 Levels of W - E - W
Ultimate whenever - obvious.
Buckshot first - obvious.
2 Levels of W so you can clear the ranged wave with Q-W combo.
I like Quickdraw second because it scales on itself. Lowering the cooldown on Quickdraw lowers the cooldown of Quickdraw, very much like Riven ultimate, where AD scales off AD... Quickdraw's CD scales off CD.
W last because it is very powerful even at level 1.
Mid Game
1. Complete your first item -- you want a Infinity before 25 minutes.
2. Position yourself well in fights, force dragon's with your early game strength Blow people up with Q-R combo.
3. Farm extremely well.
Late Game
1. Get ready to become god-mode.
2. Position is key now, more than ever, since AD Carries play the most important role late game.
3. Get your last few items.
Tip: Every auto-attack you land as a late game AD Carry is very meaningful, so feel like you've achieved something when you land any and every auto.