Mealworms, Crickets, Roaches, Silkworms, Superworms, Phoinexworms, Hornworms, Butterworms, the occasional pinky, occasion waxworms, Solider grubs, Spikes, Sow Bugs, etc.
The more variety of food items your geckos get, the better off they will be.
Mealworms, Crickets and Roaches are probably the most commonly used staples. However I think superworms and phoinexworms would make good staples as well. The rest I don’t know about, just don’t use pinkies or wax worms as staples.