Hi, Sarah:
We are all in agreement about the sand -- and with good reason. It is not a natural substrate for BTS and there is a good chance of impaction by accidentally ingesting it with the food, when burrowing, etc. Please do not use the sand with the BTS.
The size of the tank sounds great for a single BTS. It will give him plenty of floor space. They are strictly terrestrial creatures so no need for branches or anything of that sort. You may, however, want to give it some climbing structures (rock piles, upside down plastic tubs, etc.) for it to explore. A good thermometer may be very helpful to make sure you are keeping the right temperature gradient within the enclosure. Aim for 75 on the cool end and 95 on the warm end or thereabouts.
I would wait a few days at least to let him get settled in before attempting to handle him. Be prepared for urination/defecation if he feels particularly threatened when picked up the first few times. As a rule of thumb, no matter how skittish initially, they usually calm down quite a bit once you're holding them securely.
Do you know what kind of BTS you are getting? I mean is it an Indonesian, Australian, subspecies?
Any more questions, let us know and best of luck.
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Edward
Carpe diem