smlporsche

One other very important thing that hasn't been mentioned yet is to be VERY CAREFUL what modifications you make as this could bump you into a class that is not competitive for your car.
Depending on the sanctioning body (SCCA or PCA) you are allowed to upgrade to components that were offered as options on the make and year of your car.
For instance you could go to the MO 30 suspension with Koni adjustables,
Best to check before spending any $$

Serge944

First things first - replace all the wear items. That should keep you busy for a while. After that, it all depends on how much money you want to spend. I'd personally leave springrate stock until you're ready to do rear torsion bars or add coilovers in the rear