Depending on the size of your tank, Schultz Aquatic Soil from Home Depot or Lowe's or Pool Filter Sand(minimum 1mm grain size), or Soil Master Select(if you can still find it) is about as cheap as you are going to get for a decent substrate. Some members have had good success with regular 1-3 mm size aquarium gravel. In all cases, these substrates are inert which means you really have to be on top of your ferts and c02 if you plan to use them in a high tech, high light setup. Personally if I was going to use any one of these, I would only use them in a low light, low tech, setup with mainly low light plants where you have more wiggle room to screw up on water column fertilizing, especially if you keep a fully stocked tank with well fed fish and minimal water changes. The balance would just be easier to achieve and keep and these cheap substrates should be sufficient in such a setup. I am not saying you couldn't setup a high tech tank using them. I am just saying that you have to be on top of things if you do, otherwise you will be haunted by algae to no end.