Miracle Grow pre-fertilized potting soil is fine to use but you have to know your nutrients very well and be very careful not to over fertilize. Depending on the plant, you may not even need to feed during the veg cycle, the MG may take care of it. However, you will need additional nutrients to bloom the plant, and that's where you may run into trouble.

I would NOT suggest getting outside dirt and baking it. Always spend the money for decent soil and amendments or else you will regret it, sooner or later.