Here's a good mix that has worked for me many times in the past. Plus, everything can be found at Wally World & Lowe's/Home Labyrinth.

1 50lb bag sterilized mushroom compost (est. $15)
1 5lb bag black peat moss ($5)
1 box bone/blood meal ($3 a piece)
1 gallon jug worm castings ($8)
1 5lb bag of perlite ($5)

Roughly $36, and you'll have pretty much everything you need to to fill ten 12" containers.

My rough mix:

50% compost
10% peat moss (I mainly use peat to buffer my pH.)
30% perlite
10% amendments (blood/bone meal, castings, etc.)

This is pretty much a universal mix, can be used for veg and flowering, although for a flowering-only soil, I'll usually leave the blood meal out of the mix. The compost contains enough Nitrogen to keep things green throughout most of flowering, usually running low about six weeks. That's right about where you want the plants to start getting Nitrogen deficient.

Hope that helps a little bit. Also, don't forget that many online gardening stores accept money orders. It just takes slightly longer to process and receive the order. Pre-paid Visa cards are also nice and don't leave a paper trail.