You should be focusing as much as you can on farm, if you get in a trade auto attack them once and use your q. Following your auto attack with your q should win you any one auto trade.

Be careful using your e aggressive, and only do it if your sure you can win the trade or your support or jungler engages a fight and you need to position closer to get in range.

Try your best to find situations where your support can lock them up long enough for you to kill the enemy. Graves has amazing burst damage and can win most fight where his team engages or he's able to get the surprise.

Make sure at the start of the fight to activate Youmuu's if you have it, fire off a buck shot and dash to a safe location. Save your ultimate for the killing blow, it's your only long range ability and can go through terrain if your opponent tries to escape from you.

Try to position your self in the back, keep safe and only use your e defensively or when you know you won't be instantly dove for moving foreword.

You have two options with your ultimate; Use it across as many enemies as possible, which is the typical use, or save it to clean up running enemies.

If you get ran out of a fight at a few hundred hp stick just out side the fight you might find another point you can go back in even on such low hp and get some damage in.

Just try to make sure you don't die during team fights since it's critical you stay alive to push towers after the fight.