Ditto to all above. Especially the outdoor substrate. However my favorite indoor substrate is coconut coir. Holds humidity the best, won't mold and won't cause impaction should they eat some.
Where is the best place to get coconut coir? I have a 6'by4' enclosure so I will need a lot I live in Michigan and try to get him outside as much as possible but the indoor enclosure is best for at night and the winter