clearleaf

If you don't want to go expensive 'hi tech' substrates that are only accessible at specialty stores (turface pro league, eco-complete, etc), then stick with 'topsoil' or 'potting soil'. I would probably stick with anything that said 'topsoil' on the label, generally less organic materials like little bits of wood and such. Still will want to sift it out, though. Some use a screen, I used a colander.

You'll still need gravel, though, or something to cap the soil.