crickets and superworms are the easiest to gut load. silkworms are almost always a favorite. and roaches are the easiest to breed. all in all you should provide a variety of feeders. some chams are picky, they will only eat certain food. i would try a few differnt kinds and see what they like the best. some feeders should ony be used as treats,(waxworms,butterworms ect...) the are mostly fat.
I buy from mulberryfarms and reptile depot but reptile depot does not have silkworms. I get Goliath worms, butter worms, super worms, and the occasional wax worm once in a wile.
Edit :You can try and find a supplier near you and you can save on shipping.