My main ingredient for containers or if I attempt an in the ground in the greenhouse planting is peat moss for acidity and good drainage. I also use a manure/compost blend, perlite, shredded pine bark, worm castings. It's worked out well for me so far but it is a real pain in the butt for me to mix up. I always top dress with the shredded pine bark. I recently had a gentleman with lots and lots of experience with mangosteens advise me to use Promix with some sand and top soil thrown in for transplanting my mangosteen into a container. Said they get good results from that. I may try that instead of mixing unless I can find an inexpensive and less strenuous method of mixing.