1 - Rebuilt tranny with shift kit and potentially a little more converter
2 - Gears, posi, and traction aids (traction bars, latter bars, anti-hop of some sort)
3 - Biggest stickiest tire
4 - Headers, good exhaust, open element air cleaner, and recurve the distributor...maybe even a fresh set of performance valve springs and dump the rotators if the budget is at its limit
5 - See how the money holds out and go inside the engine (heads, cam, intake, stroker, etc)
Written another way
1 - Make it drive
2 - Make it launch
3 - Make it launch better
4 - Let it breathe and tune the best you can with what you have
5 - Make more power (not really worth doing on the street until the others are done)
Done this way it gets noticeably more fun with each change, without really slowing it down like a big cam without supporting parts will. If you start from 5 and go backwards, all you get is a hopping, spinning, unhappy noisemaker. I do think that with proper shopping and if you do the stuff yourself, the first 4 can be done in your budget with a little leftover.