I always use 40% Organic Spagnum Peat Moss and 60% Vermiculite (you could use perlite instead of vermiculite)

That is a perfect mix IMHO as it is essentially sterile with no nutes (so you can precisely control what the plant gets without worrying about what was already in soil too), the peat moss holds a bit of water, and the verm or per provides excellent airation for the roots and eases drainage.

good luck and keep us updated bro.

Peace