Don't lose heart. My advice would be, spend the minimum you need to make the car SAFE and preferably reliable (!) and get on into the series and ENJOY YOURSELF.
It takes a long time to get really really good at most things, so if you do enjoy the experience from the point of view of time commitment, mental prep, the odd nice move on track against less able drivers etc etc, then you may find yourself in a position to move up the expenditure ranks for a future season. The better you get, the more sponsorship you may attract...or so the story goes I believe.
But even if you don't, this is your one opportunity to do something that many of us dream about, some of us talk about, but very very few of us actually DO anything about. Seize the day, and have a ball.
You will carry a great fan club who will at least buy your beers and dinner - if you finish a race that is, they'll be gone before you crawl into the pits on the lowloader otherwise


I'll chip away at some sponsorship routes for you as discussed earlier today, and who knows what you might land up with.
Keep the faith.
Campbell