Can I equip {Illusionist's Bracers} to {Arms Dealer} and copy the ability without sacrificing another creature or do I still have to sacrifice another creature just without paying the cost?
{Illusionist's Bracers} will copy only the effect side of the ability so you don't need to repay the cost again. Sacrificing a creature on {Arms Dealer} is part of the cost so you won't need to pay that part again for the copy. As long as that effect isn't a mana ability, you'll get it twice for a single cost.
RESOLVED