When playing Graves you have to understand that you are the most tanky ad carry, Thanks to hes passive he can take more dmg then most ad carries and this make he a perfect tower diver and aggressive lane play.

The last item on Graves can be different. it depend on how you play. If you want a tanky ad carry you can go a frozen mallet, you can go a phantom dancer, a bloodthirster.

Thanks to hes passive it make him more tanky and in that way makes him hard to kill. That is why you go health runs and not armor. With hes passive Graves don't need armor runs. I go magic runes because in late game you will have a Guardien Angel and this give you both armor but not as much magic resist.

When you are farming with graves you should never use abilities to do it. Graves have a high mana cost and you should never wast mana on a minion. Save that mana for an enemy.

I would recommend always using flash. Flash is both for kill and defenses, You can flash after a kill or flash away to survive.
The second Summoner spell can be ignite or cleanse. Depend on if you wanna go aggressive or passive. If you go for a first blood or just to destroy bot lane go ignite
If you wanna just farm and taking it easy you should pick cleanse. It's the best ability to escape with.