You can make your own potting mix:
- 30% peat moss or coco coir
- 30% perlite or vermiculite
- 30% compost or soil
Easy inexpensive DIY potting mix: 50% peat moss and 50% compost.
Peat moss is available at both Home Depot and Lowe's and it costs $10 for 3 cu. ft.
You can add some 10-10-10 balanced fertilizer ($17 for 40 lbs at Home Depot) and lime ($16 for 20 lbs at Lowe's).
One relatively inexpensive premixed potting mix is available at Menard's - $14 for 4 cu. ft.
Composter Connection - How to Compost | Planet Natural http://buff.ly/1sG4qHI