Anything with worm castings and/or bat guano. Also, make sure its low on bark and has a good mix of sand and perlite in there
Everyone will give you a different answer. Pre-mixes like Foxfarm are good but expensive. Here's what works for me: 40% organic potting soil (any brand, just make sure it does not come pre-loaded with ferts) 30% sphagnum moss 20% worm castings 10% perlite