so uhh i think what makes this build good is da mobility c:
spellbinder is sick nasty cuz passive movespeed and stupid ap, plus active which gives more of both! if you got enough stacks, its like ap righteous glory!
then relentless hunter is tasty cuz cho'gath is good at the whole objective control thing with his R, but hes too slow to get to da objectives :c , relentless hunter fixes this c: , also makes your ganks better cuz they dont just have 15 whole seconds to see you and walk away.
then magic boots give more 10 bonus move speed
and approach velocity helps you close the gap after you hit a max range q, which is a problem i often encounter. it also works with your E c:

uh i dont mess with ultimate hunter cuz it only takes like 12 seconds off R's cooldown cuz its already really short so its like :/ yeah its aight but id rather not be constantly hindered by my immobility. ravenous is also cool but drain effects arent as good on burst damage champions (cuz if youre low u dont wanna go in to deal damage and thus use the drain effect, if you go in and youre full you dont benefit from the drain effect)