I agree that the first mod would be tires. Get Azenis if you're in a desert climate where rain is not a big factor. Otherwise, spend a bit more for either the stock RE010, or something like the S-03. That will set you back about $500.

Spend the other $1500 on driving schools, and taking your car to the racetrack. It will improve your car's performance more than anything you could do to the car itself.

I hear there's a good one coming up at Summit Point the first weekend in June...