If I’m trying to grow plants, I like to use Flourite. I have 2 tanks using this, about 3″ deep. I also use it in clay pots in other tanks. I think I purchased it at PetsMart.
Most of my tanks have regular aquarium gravel, or Pea gravel from Home Depot. I go for the natural colors, sometimes I’ll mix a little black in with it. Most of my breeder/grow out tanks only have a single layer covering about half of the bottom. Just enough to grow bacteria and give stuff some ware to settle until I vacuum.