I bought my car for many of the same reasons. So here is what I would do if I were to do it again.
Find a nice car, take alot of time to make sure the car is clean, in good condition, and well maintained. Don't be impatient while trying to find a car.
1st mod = Tires, mount some decent all seasons on your wheels, and buy a second set of stock alloys and mount Azenis, Kumho MXs, R compounds, etc. on them for the track.
After that, buy a helmet, some magnetic numbers and thats it. Keep the car stock. Spend an Autocross season learning the car, go to as many events in as many different regions as possible. This will let you the driver know where the car is lacking in reference to your driving style. During this time save up your money for major mods later, and fix minor things that break. Also, talk to alot of people at autocrosses, and watch other cars in other classes. Use this a guide later on.
Now that you understand the handling of your car and its deficiencies, start to mod. You should have most of your $ saved up and have a good idea of what class you want to mod your car to.
Here is a rough outline of mods allowable by class:
http://www.zilvia.net/f/showthread.p...threadid=33522
Use this to mold your car into one of the classes and start to concentrating on your driving skills, and cutting down times and most importantly, Have alot of fun.
-Matt