"Cost Effective:" You have a GL with GL springs and struts, a tiny rear swaybar, etc. so just about anything will be an upgrade. Also, when you say "cost effective" I'm guessing you've already seen the BAT kit at around $600, with most other arrangements climbing the price scale from there, and decided to look for something more "grassroots."
You could go with early SE springs on fresh SE struts, with an early SE/SVT rear swaybar. Sure to be some used SE springs out there somewhere.
You could go with SVT springs/struts. All SVT struts now are the later-spec "E1" type, which are supposedly a bit firmer than the E0 model. SVT struts, new, are around $64 each from Mr Jenkins and other discount sources. I would not go used here. Springs, though, are bound to be out there as so many upgrade to something lower.
You could go with the smaller SVT bar on the front end, which would allow a bit more lean, but would also reduce understeer.
Poly bushings are cheap, cheap, cheap. I'd put them at least on the rear swaybar. Putting them on the front would stiffen that end, which may not be what you want. You'll want to freshen up the rubber, though, if it's never been done. You'd be surprised how much these little things affect the overall feel of the car.
For that matter, it may not seem cost effective, and it's not really an "upgrade" but your front lower control arms are probably worn out if they are original. These are expensive from the dealer, but can be had more cheaply off of Ebay.
So, bottom line: Refresh the "perishable" parts and replace the others with factory pieces from the more aggressive members of the family.
HTH.
