That's a Russian tort, I'm not sure subspecies, but it looks like a lady to me. A photo of her whole plastron (belly) including the tail would make it a little easier to be sure. Definitely follow Joesmum's recommendation of coco coir or coco husk, or any of the other things found on Tom's care sheet would be good substrates. Play sand is an impaction risk and organic top soil contains plant matter that could be harmful to her.