Well, here in Brazil I never ever saw akadama with my own eyes, there is a few people who sell it on the internet, but very very pricey, as result, fewer people use it, and for a few plants...
What most people generally do around here, is a mix of simple potting soil, plus rough sand or small grain gravel (translate the granulometry is kind of difficult xD), on a proportion that varies with the species and climate, can be 50/50 for most plants IMO, but for conifers likes less organics, tropicals likes more organics, that is a simple mix to start and it is supposed to drain well, however, I've seen people mixing many other stuff, like coco coir (have used it myself), vermiculite, perlite, pumice and others, but that can come with time and practice, even because soil really depends on you micro-climate...
What works best for me, maybe doesn't for a neighboor.
Plus, most people here recommend to use general potting soil in the early stages of a tree, when you are just training them to be a Bonsai in the future, when it's finally ready to become a Bonsai, then you could think about fancy soils, and by the time, you should have much more horticultural knowledge to deal with it.
Don't think I'm restraining you from going for akadama, if you feel like, go ahead, I'm just trying to tell you that it's not required to start your own trees...