I would say focus on the engine and "safety" (old cars barely have safety anyway - the metal becomes weak), e.g., think about removing your catalytic converter ( ), better air intake, TUNING (a must), better brake discs and pads (eg Bendix), sportier tyres (don't bother with "fuel consumption" at this point") (i used potenza), lighter rims (research this properly), suspensions (if needed, strut bars), etc. Headlights and rear lights.
I would actually advice to save the cash instead of spending on a 10 year old car, but I myself have spent on my 2004 Gen2 previously.
Worthy upgrade for old car