Also look at the products from Easy Life. They have a range of products which include Easy Carbo, Easy Ferro (iron) Profito Plant Fertiliser, and Plant Sticks for poking into the substrate. So if you do decide on use an inert none fertilised substrate such as JBL Sansibar White River Sand, then you can use the plant sticks to supplement the root growth.
Or of course you could just follow the guidelines in the Estimative Index (EI) journal from Clive.
Substrate I've used them all in the past, including ADA Amazonian Soil. Personally the JBL Volcanic Base substrate topped with JBL Plant Pro soil is cheaper and just as effective.
If you use plain white quartz gravel which has no fertiliser in it or something similar, I would use a base covering of either Dennerle or the Aquaflora fertilised powder at around 1 inch deep then cover with whatever sand or gravel you choose.
Cheers,
Steve