Soil cheap?

For my grow I have almost all of my supplies the last I'm looking for is the soil. Does any one know where I can get decent soil for a cheap price or even better free. Also I was going to do a 3x3 hole with 1/2 foot of rocks for drainage at the bottom because the natural soil here is clay after 1 foot of black soil are the rocks a bad idea?

the rocks should be small if your going for drainage, pea stones or granite chips would work well or buy perlite.

The cheapest soil will be that which you make yourself.

make your own, I use a base of composted mushroom compost 50c for 6-7 gallons. Then add amendments something like subcools super soil recipe at the top of the page.

Make sure you check your local greenhouse for deals before spring hits. That may save ya a little bit, and yes by all means gather as much of it as you can by your-self. You just wanna be a little picky is all.