See those plastic beads in the soil? Those are nutrient beads. Shitty soils like MG have them.
Find the best compost you can find. Earthworm castings are best if you can verify their quality, but regular high quality compost is fine. As a general rule of thumb you shouldn't exceed 15% EWC in your mix, though some do fine with more. Next pick up some Canadian sphagnum peat moss, and some pumice or perlite. Mix them in equal portions, 1/3 of each peat, compost, and perlite/pumice. An easy way to do it is with a 5 gallon bucket. One bucket of each is 15 gal, or roughly 2 cubic feet of soil. This will be your base mix.
Once you have your base mix, you can amend it with dry organic amendments, and set yourself up for an easy grow. There are many different recipes if you look around, some using individual components like kelp, neem and crab meals, while others simply use an all purpose organic fertilizer such as tomato tone or gaia green. You may also need to add a liming component to buffer the pH of the peat, I use dolomite lime.
After you mix your soil with the amendments, you should hydrate it and let it sit for a period of a few days, to a month or more before planting in it. This isn't always necessary, depending on your mix, but it certainly doesn't hurt to let it sit for a week to be safe.
