I've worked my throat with a few toys from SquarePeg for over a decade to take bigger Cock, and reduce my gag reflex. The Supersoft silicone feels amazing down my throat. Either by training with Cock or toys, experience over time will help. If you go the toy route, be gentle with yourself and give yourself time.
As some have pointed out, some tops really enjoy their throats gagging. When spit builds up or I encounter smells/tastes that turn me off, sometimes I still gag, so you probably won't be able to eliminate it completely....which is ok. Maybe you can learn to enjoy those gags. From one oral pig to another, enjoy the growing process. 😉