I use Sunshine Mix #4 like so many others, but being on a budget, I amend it to closely replicate the Roots Organics recipe:
Lignite, coco fiber, perlite, pumice, compost, peat moss, bone meal, bat guano, kelp meal, greensand, soybean meal, leonardite, k-mag, glacial rock dust, alfalfa meal, oyster shell flour, earthworm castings and mycorrhizae.
Lignite is basically petrified peat, so I skip that ingredient. All the other ingredients are readily available, and you'll save a ton (if that's important) mixing it yourself. Plus it's really fulfilling. Also do a search in the forum for "LC's Mix." It will give you some good guidance on quantities to add of specific ingredients. Also on packaging, it's mandated that ingredients be listed in descending order of quantity which is a very rough guide, but at least logical. Harvest Moon is another respected soil mix you could alternatively attempt to replicate:
Washed coco fibers, Alaskan peat moss, perlite, yucca, pumice, diatoms, worm castings, feather meal, fishmeal, kelp meal, limestone, gypsum, soybean meal, alfalfa meal, rock dust, yucca meal and mycorrhizae fungi.
Good luck!
