Just a couple of thoughts about things I learned on my first car:
1. Just drive the car as-is for at least 2 months (3 months is better) before you spend the first dollar on modifications or accesoories. Why? To see if any serious problems pop up and require your money and time to remedy. Plus, it gives you time to gain knowlege and create a plan so you can get it right the first time.
2. Spend your time and money on 1.) learning [shop manuals, etc.] 2.) safety [brakes, steering, suspension, etc.] 3. reliability [cooling system, ignition/electrical system, fuel system] before anything else. In other words, learn and perform the basics first, before you modify anything. How are your modifications going to maximize performance if your basic mechanicals are losing performance? Or worse, what will you do if, say, the brakes fail because you didn't check/didn't know how to check that system? Its hard to modify a car when its wrapped around a tree; it really messes up the handling.
3. If you're going to do major repairs, restoration, or modification, find something else to drive while you work on this one. You can't do a major project on a car while you're using it; believe me, I've tried...it didn't work.
Please don't be discouraged if it sounds like you shouldn't modifiy the car right away and have to suffer with poor performance. If you do the things I suggested, you might be surprised at the performance you can get out of a stone-stock car. A sharply-tuned stock slant runs pretty decent, especially if you advance the distributor a few degrees.
I hope this gives you some insight. If someone had told me this when I got my first car, it would have saved me tons of headaches and heartaches, as well as making my efforts much more successful and a lot more fun.
Congratulations and good luck!