Should you use small stones/rocks under a deck, or leave it bare w/dirt and gr?

I am thinking about intalling a freestanding/freefloating 10x24 low deck which goes from the middle to the corner of my house, and was wondering if putting down small rocks/stones and tampering them down then putting my deck on top of it by using about 25 of those Dec-Blocks? Im just wondering if that would make it more stable, maybe help with drainage, or do most just install freestanding decks on the bare ground?