Stoped buying soils few years back, my loved 110 liters soil bags are not available anymore, they was cheap and nice soil, I looked for others soils and it wasn't cheap at all, so now I buy perlite, coco bricks and worm castings, I go near forrests and places where I know there are nice soil and take some big buckets (if is necesary sift/sieve the earth avoiding clay wich is more thin and medium/big stones), depending on soil type, I add more or less perlite and coco (around 20% or more), I mix the soil and perlite/coco and then i add old and dry grounded cow manure, a lot, something around 30% or 40% (if summer pass by the manure, it will ok at 8 months, need to be old, better 1 year+), cow manure could be the more easy to get, there are cows everywhere in almost all countries and they pop a lot xD Then, every season I top dress cow manure, worm castings and some bat guano in preflowering (100-200grs/plant), you really don't need nothing more.