Cresties are fab! They don't need bugs - Alan Repashy has developed a crested gecko diet (often abbreviated to CGD) which he has fed his breeding geckos on for decades without the need for bugs. I feed
Repashy's CGD as it was recommended to me by Errol's breeder as the best. There are others out there, but Repashy and Clarkes are the best. Apparently most cresties aren't a fan of zoomed which is often found in pet shops. It may seem expensive, but I bought 2 4oz packets a year ago and there's still almost a whole packet left! I change his bowl of food every other day - it smells lovely and fruity (I have mango and peach, but recently they changed so there's only one tropical flavour).
I do also feed crickets (usually a few times a month) as it does give Errol exercise. Crickets need to be dusted with Nutrobal powder. If you feed crickets in the vivarium, you have to be careful with substrate and have one that can't cause impaction if swallowed. I use reptile carpet as I find it so much easier to clean than the coco fibre and orchid bark (which you shouldn't use for young geckos).