Hows your mechanical ability? Cams can be had for $300 used. Installing is a different story. A shop might charge you $300-500 for installation if you can't do it yourself.
1996-1999 S52 M3 Cams = $300 (20-25 hp)
1992-1995 M50 Manifold = $75-125 (15 hp)
Cold Air Intake (Cosmos V1/V2) = $75-150 (5-8 hp)
Traction contol delete boot = $20 (3 hp)
Cam specific software = $500-675 (You can have the stock DME burned or buy the seperate and uninstallable Shark Style Injector)
Standard Shark Injector = $375 (Will do about 75% of what the Cam software should do)
Custom Exhaust = $300 (5-7 hp)
Pulleys = $150-250 (5 hp)
Fan Delete = $90 (3-5 hp)
Don't just add all of the HP estimate up to get a total. After adding the cams, M50 manifold, and software the rest just work to optimize the flow of the engine with no major gains. With all of the above you should see around 225-230 whp and over 200 ft/lbs of torque. This would make you faster than a stock and on par with a lightly modded M3.