My first 'major' project was writing a Lisp interpreter from scratch. Looking back on it, my implementation was horrible, the design atrocious, and the extensibility null. However, I remember how AWESOME it was at the time to be able to run my code on my own interpreter. What mattered most about that project wasn't the program itself: it was what I learned in the process. I guess my point is, no matter how shitty your code is, you learned something from writing it. So don't wait for a 'firm foundation' to start hacking away, just dive in and feel free to screw up. Just don't screw up in the same way the next time you do it.