It depends on how far you want to go. I have a few mods on my car none of them really cheap.
Looks wise you can:
Bigger wheels/nicer wheels ($$)
A good detail ($$)
Leather interior ($)
tinted windows ($)
Lower it ($$$)
New suspension set up (dampers and springs - loads of info on this here) ($$$)
Better pads and brake fluid ($$)
Anti roll bars ($$$)
V6 induction pipe mod - google it its everywhere ($)
I have done all of the above except the new muffler and it does add up. ive spent twice what the car was worth when I bought it so modding is extremely uneconomical but If done right gives your car a fresh breath of life. Im currently saving up for a wizard exhaust on my car hopefully sometime soon..
Personally if I were you i'd focus on the car being mechanically A1. No amount of mods are going to make your car reliable. Good service, cambelt whatever needs doing. The most bang for your buck mod would be upgrading the suspension and lowering it, followed by the thicker arbs. Both are expensive but massively worth it IMO and have transformed the car.
The rest is entirely upto you mate and what you want out of the car. Everyone is different and want different things out of the car. I do a lot of driving round australia and sometimes my ride makes it a bit annoying as its quite stiff but get to the twisties and all that annoyance goes away