I would do the exhaust and struts/springs first.
Exhaust not only helps power, helps mileage, but also sounds nice too ... this really gets you the bug!
Struts/springs, just taking a guess here, but if you haven't already replaced them, I bet you're not far off needing them. Guessing from average mileage on a 1999.
Do these two first, and you'll enjoy driving her so much you'll start planning to mortgage your house for the rest (I did, but wifey spend the money
).
You'll probably want to throw on a filter too, as it's an easy mod, and relatively in-expensive.
**Edit**
Don't forget to change the trans-fluid if you're an MTX75.
