Red,
I would go with a smaller cage. He is going to have a hard time finding food and water in such a large setup, esp with how heavily you planted it. Put him in a small plastic (see pic, ignore the moss tho) critter keeper and move him up while he grows. He shouldn’t need a 10gallon until he is at least 6 months or so. As far as substrate goes, if it’s big enough to fit in his mouth, it could cause problems. The keyword there is could, it can, but it’s not common. To be on the safe side all our adults are housed on paper towels. Not the prettiest but cheap, safe, and easy to clean. However since your guy is just a baby I would leave the bottom bear and keep the setup simple, just a branch or two and a tiny piece of silk foliage. This way crix have no where to hide and your gecko can easily hunt them out and get his fill. When he hits that 10 gallon you can use paper towels (see other pic). If you want to use something natural, either make sure it’s not big enough to fit in his mouth or use bowls. Just pinch the back legs off the crix and place them in to a small dog crock. For more info just drop me an e-mail (address is above) and I will send you an interactive care guide for crested geckos, should answer all your questions 
. Best of luck and welcome to the forum!
-Mike
gexfiles
