There are at least two approaches to indoor substrates:
1) Easy to maintain: Newspaper, builder's paper (looks like the material used for grocery bags), aspen, carefresh, indoor/outdoor carpet, etc. The cost ranges from free (newspaper) to kind of costly (carefresh-type substrates). But it's easy to keep the bacteria and odors under control. Flat layered substrates (newspaper, etc.) fail to provide a place to burrow, something which tortoises need. Can be improved by providing a hide box.
2) Natural: Soil, sand, peat moss, coconut fiber. Looks better, gives the tortiose a place to burrow at night, helping it to retain heat and moisture. But it makes it hard to control the accumulation of feces and other wastes, eventually leading to a buildup of bacteria and odors. Requires constant maintenance (look for feces) and must be changed regularly.
If you have only one tortoise, then a natural substrate may be OK. Multiple tortoises in one enclosure can really make a mess. For a russian hatchling I used sand mixed with plain topsoil (no chemicals, etc. About $2-$4 a 40lb bag at Home Depot). If you are using sand with something else, mix them together thoroughly. Using sand alone actually worked better with my hatchling since I could easily distinguish his droppings from the topsoil. Since sand is very dry I would lightly mist the substrate once or twice a day, simulating dew or a gentle rain.