You are wise to plan a bit of practice work before starting on the good stuff. Like Jason above, I made a 10V on my Unimat…the castings came with the lathe..but before starting I made a simple oscillator for practice. If something like that does not appeal, why not make a few simple accessories for the lathe, like a tailstock die holder, knurling tool, and so on. There are plenty of simple things that will come in handy later, and it is better to make your first mistakes on something easily replaced.
John