My favorite dirt

When creating ground cover, a lot of people like to use real sand, baseball diamond sand, vermiculite, or other natural sources.

My preference is to use the artificially colored sand that is sold at craft stores, and typically used for sand art, sand in bottles, candles, etc. The bright primary colors won't do you much good, but if you stock up on white, gray, a couple of shades of brown, and maybe a dark red, you can blend 2 or 3 together to get some quite nice shades for ground cover.

It looks even better if you mix in some fine green ground foam, and maybe a little fine ballast or talus to simulate the occasional rock.