Well, first of all you will start to build your boots (the recommended one).
After you got the boots up then you start to build a phantom dancer.
When it is done go for a infinity edge.
After it, you should start to build a blood thirster.
Then a phantom dancer again.
And after it you build the warmongs so you get some health.
Last item that you gonna build is a black cleaver.
Remember, as a AD carry you will need all the minion kills, so a tip is that you go with a support/tank.
You need to focus the minions so much you can, but if the enemy comes near you then you need to start to attack her/him with the Q, Q is one of the spells that criting most on graves.
When they trying to flee with low health, then you use the ULTIMATE, but it is good to use it in ganks to.
The E is good to avoid things, like veigars ulti and to run back. It can be used to get threw some walls.
The W, is a smoke screen that doing so the enemy can't do spells and will slow them down.
Also a good combo is E, Q, W and then the ULTIMATE.
Good luck and have fun with this build!