When I got my first bonsai in 1964, there was no internet to shop on (no home computers even) and there were no bonsai dealers in all of New York City. I learned to make bonsai soil from a simple formula in "Sunset Bonsai" a book (now out of print) that taught me more about bonsai than any single book since. The formula for evergreens was 2 parts sand, 1 part topsoil and 1 part peat moss. For deciduous trees it was equal parts of the same three ingredients. It worked, but it didn't drain too well, and it compacted after a year or so. Over the next 25 years I added and deleted ingredients, changed proportions here and there, and by the early 90's I had arrived at the "recipe" I have used since. It is a mixture of 14 ingredients. It has great drainage without drying out too fast, and it doesn't compact. These three features, in my opinion, are critical to a good bonsai soil mixture. Drainage is essential because, while bonsai roots need constant moisture, wet soil can cause a number of problems. The trick is a mix that stays moist but not wet, and dries slowly. A good bonsai mixture should never compact because that will make root growth harder for the tree, and repotting more difficult for the hobbyist and more stressful for the bonsai. Many people who have tried my soil said that it was the best bonsai soil they had ever used. That makes it worth the time and effort I put into making it.