If you are on a budget, then Coil-overs are out. Use Bilstein shocks, for springs look here for info (
http://www.maliburacing.com/coilspring.htm). Many use the S10 springs for a lower, stiffer ride. Find a 36mm hollow front F-body sway bar ( Ebay). The Grand Prix Jounce Bars are a good addition as well. A reasonable brake upgrade is the Blazer dual piston upgrade, and I highly recommend it. Replace the bushings if they are bad, and check your ball joints. Do the Jeep steering shaft upgrade. For the rear, add a sway bar if you don't have one ( Monte Carlo SS), Bilstein shocks, and springs from above. Again replace the bushings if they are bad. You can replace the control arms with aftermarket, but may not see much of a change for the money, unless you run at the track. You can add disk brakes, but they really don't add much over the drums, since the front brakes do most of the work. Can't give you much advise on the wheels- I've only got 16's. I know the larger you go, the lower you have to go on the sidewall ( Aspect ratio). This reduces comfort and the ability to absorb shocks like Pot holes, etc.