Getting a baby uromastyx this month advice needed. Help please read!

I am getting a 4x2x2 pvc enclosure. I wanted to get a baby and was wondering if I should keep it on paper towel before introducing substrate or can I just have substrate? I also am planning on getting a 14% Arcadia uvb 22inch light and a 100w hallogen bulb. For substrate I wanted to use reprisoil play sand and excavator clay. Just need advice on if this stuff is okay.