Hello Anon,
If you are planting tropical succulents adding some of that orchid bark mix with cacti mix soil will be good, these types of succulents love just a bit more moisture than the others.
But for my other succulents, I just use super soil palm and cactus mix, I get them from Home Depot. Then I further add pumice or perlite in the soil, since most of my succulents stays outdoors and we get some rains during winter. Got to make my soil media very well draining. Recently I also top dress with chicken grit (insoluble crushed granite).
