Bark mulch isn’t the best idea for succulents; it holds too much moisture, especially in the winter. I wouldn’t put down any mulch until you’ve been able to get the weeds pretty well cleaned out. (Try applying Preen or corn gluten as you go.) Pebbles would look great eventually; but they’re a pain to weed, and everything under the sun seems to love germinating in pebbles. There’s also a stone grit used for walkways – I have a bluestone grit in my garden paths – that might work.