If you can ride along in other cars with various changes to feel how they work, that can help you target your changes towards your goals.
Start with the obvious - replace any worn suspension or steering bits. Old, stiff, and cracked rubber bushings and loose ball joints add slop into the suspension and make the car ride weird, handle badly, and make it generally no fun to drive. To state the obvious, if worn parts go too far, the car becomes downright unsafe. Use good quality parts - cheap stuff is usually cheap for a reason, and replacing suspension parts is not something you want to have to do regularly. My steering shaft was very loose, and in my case that helped more than I expected.
Next, the specific shocks and struts you pick will matter a lot for your ride quality and handling, and if you have worn shocks/struts, replace them. Cheap no-name shocks and struts rarely perform as well as you want, but sometimes you get lucky. This is a huge topic if you dig into it - shock valving can be customized in lots of ways. You can spend a lot for double adjustable shocks/struts to tune your suspension easily, go with a known high quality aftermarket brand (Koni, KYB, Bilstein, etc.), or you can pick a good quality replacement set at a more reasonable price. For example, I really like how the OEM Bilstein shocks/strus on my Challenger ride (they are equivalent to the aftermarket B6 versions, IIRC), but I might like a firmer ride that you do. That's also a much heavier and larger vehicle than my Mustang, so may not be a direct comparison.
Next, pick the right set of wheels and tires for your goals. Low profile tires handle better, but do so at the expense of ride quality. If you've ever had the chance to try something like different diameter wheels with equivalent width tires on the same car, the difference from the shorter sidewall tires on larger diameter wheels is
very noticable. The short sidewall tires on my Mustang ride like rocks compared to the tall sidewall tires on my Suburban. The Suburban tires soak up a ton of bumps, but also make it ride very soft and squishy - I think they're
too tall, at least for what I like. Even the brand of model of tire can make a difference in comfort, and they will absolutely make a diffence in your available traction. I find tirerack.com does good tire reviews and they have a lot of purchaser reviews as well, but they are sometimes biased towards all out performance vs other tradeoffs.
Beyond this, opinions will vary. It matters how much you want to do to the car and what your budget is.
I'd recommend subframe connectors as a next step (if you don't have them already), especially if you have a convertible. If the car itself isn't stiff and stable, the suspension can't do its job right. My '97 was a felt a bit like a wet noodle before I put in subframe connectors - feeling and in some cases seeing the body flex over things like railroad tracks was crazy. It helps make the car drive better and let the suspension work better - for my car this was one of those rare all around wins with no compromises.
Beyond this, all of my research says that a good set of coil overs is the next step for the front of a Fox or SN95 Mustang. A big box of parts from Maximum Motorsports for my '97 is on my todo list once other projects and emergencies stop draining my bank account.
They offer free consultations and will help you spec out parts to go as crazy as you want to - I have been very impressed with them so far. They are total suspension nerds and it shows. I found their tech pages very helpful - they helped explain things and gave me a lot of food for thought about how to proceed with my project. The consultation I did with them was also very helpful.
