you should try any cactus that is a jungle cactus, and i am thinking quite a few of the opuntia's would grow , poorly , with little light in a terrarium. Cinta is correct however, you should be looking for succulents. You will need to be very careful watering cacti or succulents in a terrarium as it will act as a very small greenhouse, ie heat fast and stay humid with mass condensation. as far as soil i would use one part potting soil to two parts lava rock or pumice or even just styrofoam packing peanuts. The trick is soil that water will move through quickly and have a deep layer for the water to go.
