Graves deals mostly physical damage so Armor is an effective counter.
Leaving the Smoke Screen's area of effect removes the harmful effect immediately.
Given how his auto attacks works, they can be intercepted by structures and other units (champions, minions, and monsters). This can be very useful when skirmishing.
Always aim to hit End of the Line against walls when going against jungle monsters and enemies, as this will deal both instances of damage very quickly, catching most enemies off guard.
End of the Line is a very strong wave clear tool. Minions cannot dodge the second attack, and a few autoattacks followed by End of the Line will often destroy an entire wave.
A waveclear combo is for Graves to use End of the Line usually leaving the caster minions with just a sliver of health, using Smoke Screen to finish them off, and using autoattacks to kill the melee minions.
Smoke Screen is a powerful denial tool. Enemies inside can completely not see out and are slowed. Work with your team to make sure to install this vision denial on the enemy for as long as possible, as they cannot return autoattacks if they are within the smoke.
Quickdraw has various uses. It can be used to dash over walls to chase enemies or to escape, or used as a gapcloser to secure a kill with an autoattack, or can be used to reposition End of the Line to hit a wall.
Death's Dance provides AD, CDR and two useful passives that heal Graves for physical damage he deals and pseudo-damage reduction.
Phantom Dancer gives AS, Crit Chance and MS not to mention a passive that gives more MS and damage reduction against the last target attacked which is useful for kiting, chasing and dueling.
Maw of Malmortius is a good defensive choice against mages and AP assassins as it has MR and upon reaching low health, a magic damage shield along bonus lifesteal and spellvamp for as long as Graves remains in combat.
Sterak's Gage is an alternative for defending against massive burst damage in general with its health and shield when taking high amounts of damage.
Take note that the passives from Maw of Malmortius and Sterak's Gage are both classified as the unique passive, Lifeline, and as such do not work together.
Duskblade of Draktharr provides a high amount of damage with AD, ArPen, MS and an execution passive. As it doesn't give any survivability and has a high cost, this item should be bought only when snowballing.
Berserker's Greaves are the best offensive boots for Graves as he can use the AS from it fairly well.
Mercury's Treads, Ninja Tabi and Boots of Swiftness should be bought accordingly for their defensive properties. Bear in mind that these options provide no damage and should only be purchased when in dire need of them. For the most part, the resistances from Quickdraw should suffice for tanky stats.
Lock Graves down before he can use Quickdraw to escape.
Pick a hard engage champion to lock down Graves before a fight begins. If he lives for a long time, he deals a lot of sustained damage.
Choose a reliable dueling champion who offers a lot of hard crowd control, such as Poppy or Malphite.
Graves is a huge lane bully. Melee bruisers will have a very tough time against him.
Do not underestimate his early game damage. He often wins both short and extended trades if he is not stunned.
Graves is deceptively tanky with Quickdraw's True Grit coupled with the common bruiser build path of Sterak's Gage and Maw of Malmortius, so take care when trying to assassinate him. He might take more damage than you expect.
If he is caught reloading with no shells, he cannot autoattack until he finishes, so feel free to engage him. Beware though for he can instantly reload a shell with Quickdraw.
Stay away from walls when fighting him. Walls heavily reduce the proc time of End of the Line's return damage, leaving almost no time to avoid both instances of the ability.
Graves's shotgun deals an insane amount of damage at close range. Stay away from him when fighting him, as he can deal as much damage as a melee at low levels with just his autoattacks.
He is a very strong splitpusher as his shotgun can quickly kill turrets if left unattended.