Originally Posted by Fawnleaf
so are the airstones+tube+pump expensive??
They are relatively cheap, but totally unnecessary. The big purpose is to add oxygen to the water and in some cases, such as with undergravel filters or sponge filters, to create current to aide in filtration. Bettas don't need highly oxygenated water and the plants in a planted tank actually create oxygen so it is unnecessary. Your money will be better spent buying a substrate for your plants (and the plants themselves)
With a planted tank you almost always will want a substrate. A substrate specifically designed for plants is even better (fluorite, ecocomplete, exc.). As Alex suggested their are some plants that don't need it, but your choices of plants are much better if you have it.