I would usually advise against a dish of calcium with D3 added. Geckos should always have calcium available free choice, but it should definitely be the type without D3. As for your gecko, I would say that you could feed every other day (since he is by now a full-grown adult). You can feed a large array of insects, but make sure that those insects are captive-bred, not caught from the wild. Some common feeders are crickets, mealworms, superworms, butterworms, and phoenix worms. Make sure that you dust the feeders in calcium powder before feeding them, as well. You can dust them in calcium with D3 once or twice a week, depending on your preferences.
This website also has a ton of very helpful care sheets, located in the care sheets/articles subforum.