Buy track insurance and you're covered. Some insurance companies will cover it but there is a whole different thread about that...
Or find a cheap E30, put a little bit of money into it and if you ball it up for the most part you're not out too much. That is what I've done and IMO the E30 is a MUCH better platform to learn on than the E9X M3. A bit more "analog" than "digital" and it forces you to become a better driver I feel.