Layering planted tank substrates doesn't really help to any proven degree that I have found or read about. It only adds complexity and frustrations when all of your layers end up getting mixed together eventually.
Use a complete substrate of Flourite or Eco-Complete would be my recommendation.
If you look at some online contests for planted tanks, around 75% of the tanks use 100% Flourite. That convinced me from the beginning to use that.
Do a Google search for "planted tank contest" and look at what the various people have used in those tanks for substrate. Then decide for yourself.