I feed mine Rep-Cal.........they are juvies.......however I feed them crickets and mealworms also! With a side salad about once a week.
You can get them used to the prepared food then put crix or mealies on the prepared food and they will usually eat it no problems.
You will have to feed them insects a few times a week though if you want a healthy happy dragon!
Believe me though, THEY ARE SOOOOOO WORTH IT!