^^^^^^^^^^ Theres a million answers to that question, and here's mine.
40% FFOF, 40% Happy Frog, 15% perlite with worm castings, blood meal, bone meal and dolomite lime making up the last 5%. Works great in a 12/12 from seed setup, no nutes for 50 days and then just banana/molasses/bat guano tea til harvest. Simple, and since you used no chemical nutes ( ie organic ) you can recycle your soil.