Initially, I would spend my money on suspension upgrades, replace all bushings,etc, get it to handle, and spend some time on the track learning how to drive the car. Get some better brake pads as well.
Then I would start on the slippery slope of power upgrades, either go back to a stock spring or make the intercooler the priority buy, it will be cheap insurance. Also make sure you have your AFR's where they need to be, again cheap insurance.
1986 930 (Gone but not forgotten)
2007 BMW 328Xi Sport Wagon