There are 3 things you should replace and you'll notice a huge difference, two of them are a pain in the ass to replace. 1) rear trailing arms bearings (4x, 2x per side), bearings cost less than $30 but replacing them is a lot of work. 2) strut bearings (4x) front and rear less than $100, go for any reference supplier (Lemfoerder, Meyle, equivalent) just stay away from Febi/Bilstein they're useless. 3) Front wishbones including lower control arm bushings and stab control arms should run below $300 and well worth the invest. Springs I'd go for Eibach any time of the day, alternatively red H&Rs 35mm or less they're below $80 most of the time (good used ones are fine). Biggest ticket item the shocks, I run Bilstein M-Suspension ones and had them for 150k mls+ they're still as good as new, even used ones are around $350+ so try to find a good deal on those - they make the ride quality.

Stay away from polyurethane bushings/bearings and springs lowering more than 40mm - they ruin the ride and don't provide any real life benefit.

In total you're looking at ~$500 without or ~$800+ with dampers. From my own experience I can say do it all at once or wait to do it all at once :).

Without the rear control arms you're done in less than 4hrs with some help. The rear control arm bushings add a good 8 hrs mainly because of disassembly and the tedious task of removing and installing the bushings out of and into the control arms. Once they're in they last for 200k mls.