I agree with Nico. Mainly because that's exactly the approach I've been using this past year.

Nico I know you know all this but just for the benifit of the original post.

I started the season with a very under prepared 1st. Gen RX7. It had a bolt in cage, header, fuel cell, seat, strut brace and kill switch. With the help of a lot of MiDiv folks I've been making improvements over the year with the goal of just getting as much seat time as possible since this is basically my first year. Most of the money went into suspension and brakes. I did have to replace an engine after that last event at Hallett, but at over 200K miles and 8 years of racing the old engine was bound to go sometime. I got a little better each event and still have some development to do on the car this winter.
I'm certainly not an expert on the issue by any stretch of the imagination. If you have the money to do all the stuff to your car you want and still get lots of seat time then go for it. If not, make the improvements your budget will allow and still let you get the seat time. I, for one, don't have the funds to make all the changes or upgrades I want to make and still race and I can't think of anything worse than having a car that might be competative and not being able to race.

Monica kicked some serious a** against GT cars at the last event at GIR.