I've taken a lot of mine apart over the years so the main things I've noticed from age/miles on mine specifically are:
Rust on corner of the sills both front and back, damp foliage makes it way behind the arch and can slowly rot it out a little.
Dampers if original may feel okay but taking them off the car I realised they were toast (the rears literally had no rebound at all
Cracked springs.
Bushes are still MOT worthy when this old I've found but Soft like marshmallows from age and nasty muck and oil.
Engine is great but Cam follower needs checking/replacing and injector cleaning/valve blasting is not essential but gave me a smoother idle and possibly released a few ponies when tuned.
Dipstick broke into sump so needed to be dropped and cleaned and clean the pick up pipe while it was off as a why not.
Thermostat broke so car could not get up to temperature when on any kind of highway doing 50mph+.
3 fuel injectors died.
Diverter valve went which created a boost leak.
Rocker cover gasket went which created another boost leak
Exhaust after the main cat was looking quite holey and came up on an MOT.
Siezed rear calipers.
Those are the main issues I've seen on mine, some other stuff that's too trivial to mention. Obviously you might find one where everything is perfect this is just what I've found on mine and I know others on here have had some of these issues over the years also. Age takes its toll eventually!
Your budget depends on whether you want to upgrade old parts or just replace with oem/aftermarket.