Ok, so I see why your struggling with this build, back in season 3 (Before they nerfed BT) this build may have worked, but now it's outclassed pretty heavily. On most ADCs, Graves included, the build is this:
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(get this item if the enemy mages become a problem, or they have a lot of poke. e.g.
) or
(for when the enemy team has assassins, this helps because once the assassins blow all their spells, they have to wait and kill you again, giving your team time to help you out.) or
(If they have lots of cc, or suppression ultis. e.g.
) or, like another poster has commented, getting an additional
will maximize your dps, but I would recommend against it, as this leaves you without any defensive items, and as a squishy ADC, you really need some defensive stats.
I hope this helps you out!