Improve the feel of your ride with new shocks
Price: Varies by car, but expect to pay at least $600 for something good
Shocks are often overlooked in pursuit of bettering your car, unless the end-game is performance, but in truth a good set of shocks can absolutely transform your ride -- that’s why they’re called shock absorbers. Depending on what car you drive, expect to spend a few hundred on a really good set, either online or at your local parts store. If you're uncomfortable changing these out on your own, a good shop shouldn't take too long to do it, and you'll notice a huge difference.
Get rid of squeaks and ride smoother with new bushings
Price: Varies greatly, but starts around $50, and runs into the hundreds
It sounds boring, but if your car is getting up there in age, worn bushings -- which serve to mute the vibrations coming from the engine, transmission, and the car’s interaction with the road -- won’t do their job properly. Assuming everything else is in good condition, some fresh bushings can make your car feel like new again. For the most part, you'll want to have your mechanic do these, though, so keep labor costs in mind when you're determining how extensive you want to go.