Well, trying a Das as a bonsai is a great way to practice many bonsai techniques. They are inexpensive in the smaller sizes. You can find them everywhere in many parts of the country. They seem to be somewhat forgiving of most horticultural mistakes in many climates. All the ones I've see have been the standard, single trunk, upright, conical shaped ones. Not only are you able to do root work right out of the pot (so to speak) but they are great trees to practice design ideas, shaping, foliage removal, wiring and wire removal. With some slightly older ones, a person could even try bending the trunk with rebar or even using a branch bender. It's also a good way to inexpensively experiment with some more extreme techniques.
Isn't that a great way to start to practice?
I know there will be some arguments to start with better material to learn good techniques, just as there are to use copper wire instead of "sissy wire".
I hold a strong belief that anything that saves money to allow the purchase of more and better tree material is a good thing.