Floramax doesn't have nutrients, and you do have to make your own mineralized top soil.
My advice, the same advice that I ignored when I started and wished that I hadn't, is buy some ADA Amazonia I Aquasoil. The stuff is amazing, it's not that (comparatively) expensive, and it will give you lots of leeway with growing healthy plants.
There are some other good alternatives, but you won't find any of them in Petsmart or most LFS
. Fluval stratum, Mr. Aqua planted tank/shrimp soil, Azoo plant grower bed are all supposed to be good, and are around the same price.
The great thing about these substrates is that the nutrients are already where they need to be, and you don't have to worry so much about fertilizing in the beginning. Not having ferts in the water column will also give you more lee-way with algae problems, at least for a while.
Mineralized top soil will do the same thing, but it is definitely not a quick easy DIY. If you're on a budget, MTS could be your best route.