Fast draining and very, very light on the fertilizer is what works for me. The roots rot if the soil doesn't drain well.

Totally agree. Every one of my potted plants from thirsty Coleus to a Euphorbia are in the same "stuff." If water comes out as fast as you can pour it on, it's well drained. If it builds up in the pot, that's not well drained. Simple as that. How to get from here to there is the subject of debate, but that should be your goal, whatever you actually put in the pot.