Well I had Knights of the round around the time I fought carry armor as in I mastered a few all materia's right outside of Mideel then proceeded to get a Gold Chocobo as soon as I sold 2 or more all materia's.
Yep, movers and magic pots in the swamp areas of the crater. I usually use my save crystal there so I can save and keep grinding, and the use of tents is quite nice.
Don't expect to master a KotR materia without about three hours of straight grinding though, even in the swamp. However early game materia like bolt and mystify and shiva, you'll master so fast it's not funny. Equipping the armlets from bone village that have double materia growth and using Cloud and Cid in your party is recommended. Cloud has a sword that gets triple growth with three slots, and Cid has one with triple growth in two slots and another with double in five.