Savanna monitors are pretty cool but you really need to work to get them tame. They eat a lot and will get fat if you aren't careful. 6' by 3' is decent size cage for an adult savanna but I would go 8' by 4' if you have the room. They are burrowers by nature but I haven't seen many that like to burrow myself. Basking lights with a basking surface temp(Pro exotics temp guns rock!!) of 110-130+ degrees. Keep the cage at an ambient of no lower than 70 degrees(75-80 is better). Humidity in the 60% range is fine and they will hold lots of humidity in the burrows. Just plain old dirt from an area of no pesticides is awesome!!! 2'+- deep is good for the burrows. Just be ready to order bulk frozen mice because they can eat a lot!!! My boy would go through 5 mice in less than 2 minutes every other day when he was still growing. In all, awesome captives if you have the time and space.

As for a good starter monitor I would go for ackies. None ever get bigger than 3' and very rarely much over 2'. Like it hot and are mainly insectivores.

Hope this helps a bit