try buying some organic books and skunk magazine theres always beginner recipes in them, and off those you can make new ones, once you do some research and have simple understanding of the biology going on in soils ecosystem
try sunshine mix its the simplest to go into and has plenty of beneficials it comes in bales, the after youve rooted in a small amount of soil give them something like a compost of ocean forest by foxfarm is always my choice. be careful to much and you burn your shit up, this soil is really hott...
expanded clay is best used in aquaponics, not to be mixed with soil, alot people do this, i hope you bleach them after everyuse, otherwise they could be the start to and fungal problems u might have, if any. Dryness is good thats how your roots grow, use bigger pots if they are getting to dry...