Boil it down to the fundementals:

Do you want to win? Do you want to learn? How much money do you have to do that?

The answers to those questions will define your actions.

If you want to win, then you'll have to get a car that can do that, AND one that meets your budget. I doubt you can build a car that can win the ARRCs in ITB for the $8K that the winning Accord (05) was on sale for.

If you want to learn, then your budget requirements can go down a bit. Those RX-7s can be bought in the $4-5K range for good cars. And they are cheap to run.

Building your current car up to specs/performance (is the cam legal??) is likely going to cost you more than the end result will be worth, and keep you in the garage, rather than on the track.

And ...no offense intended....but the one area that improved the most in my build (and I hope continues to improve) is the driver. Money spent on the driver...as in driving..pays off. keep an open mind, learn learn and learn, and you'll be surprised how fast these cars can go. The fast guys at the front are really fast when you get up close and watch what s going on.