600-800 is ideal budget for new cup shocks, eibach or sportline springs, and a refresh of the bottom arms / steering components etc.
We did that on my mrs old 172, then did about 50 trackdays in it and a 5 day trip to the ring and spa.
The ONLY place it ever really felt compromised was Spa, its was brilliant fun everywhere else and great fun on the road.
Sure compared to some of our other cars on coilovers it lacked ultimate corner speed, but people get confused between grip and handling too often, while it only gripped "ok" it handled "very well" IMHO, was very controllable and great fun.
Out of the dozens of dedicated trackday cars I have had over the years, Im not sure any one of them has ever brought me more pleasure overall (when taking into account reliability and not needing to trailer it around and all those things that can detract on the more dedicated cars) than that well sorted 172 with such a basic spec, these really are epic little cars when all in good order, they dont actually *need* anything else to be great fun on a trackday, and it did 30,000+ road miles as well so was useful as well as fun.