I agree with RIcCorey and purpleinopp. I buy a decent potting mix (12$ huge bag) then further cut it with fine bark ($4 huge bag). I use Kambark from the Ace stores here on the East Coast (elsewhere too?) Seems kind of silly to buy all the special ingredients just so you can make good potting soil? You can buy some excellent potting mix if you hunt for it. (Fafard made a good one, are they still around?)
Do read tapla's advice for understanding of what makes good soil.
