Try to keep your True Grit stacks up by attacking minions, for free damage mitigation.
During the laning phase, Buckshot is a strong harassment ability, but will quickly drain mana if used constantly.
Using Buckshot on caster minions will kill them in a single cast at higher ranks, even without damage items.
Graves can push and farm a lane easily by using Buckshot. However, Smokescreen should be reserved due to its relatively low damage, and high utility.
For a high damage combo, throw a Smokescreen on your target, close the gap with Quickdraw, and fire a close-range Buckshot.
The sight reduction of Smokescreen has great utility, along with the AoE slow.
Smokescreen can be used to juke your enemies and allow Graves to make decisive choices when either chasing or escaping.
It can be used to set up a gank, because the target will not be able to see any incoming champions.
A Smokescreen can be a strong deterrent for an oncoming enemy team.
Smokescreen greatly diminishes the utility of an enemy champion that relies on skillshots, such as Xerath or Lux.
Graves'sQuickdraw can be used to dash through thin terrain. This allows Graves to be very mobile and can benefit him in chases and escapes.
Try to use Collateral Damage at the beginning of a teamfight when your enemies are grouped together, allowing you to hit multiple targets.
When the champion against you has a blink (eg. Ezreal), and he attempts to engage you, throw a Smokescreen to where he blinked, and quickly dash away leaving your opponent visionless.
By using smart cast, you can cast Buckshot and Quickdraw together in such a way that you dash back while shooting the three bullets of Buckshot in front of you. Use this combo to finish off enemies with low hp and make a quick escape.
One of Graves' strengths is his burst. Try to avoid his high burst and take advantage of his high cooldowns during the early game.
Consider investing in early armor to mitigate his damage at early game.
Try to spread your team out, to minimize the damage from Collateral Damage.
Quickly move out of Graves'sSmokescreen. The debuff only last when you are inside the AoE.
Also, save your spells until outside of Smokescreen as the vision loss can lead to the loss of your target.
If you are a champion that plans to cast a supportive ability on an ally, considering staying close to the ally so that Smokescreen cannot stop you from seeing them and thus casting onto them.
Avoid extended skirmishes with Graves as he gains armor and magic resistance as the battle rages on from True Grit. The bonus armor and magic resist can change an expected kill to a close call.