Your best bet is to start with an all-purpose media, I use only MiracleGro Potting Mix. MG makes a ton of different dirts so make sure you get the PM. Most all the "starter" soils I've tried were much too thin to be beneficial. The MG PM is formulated to feed a plant for 3-6 months so you know your gals will be getting all the basics without you having to tweak anything. The MG Potting Mix has 15% perlite included for moisture control so you are already good there. Go ahead and mix in some worm castings if you need to do something to the media. Personally, I trust the pros and keep my labor to a minimum at the same time. BigSteve.