[xxxalexxxx]

Like others have said there is no such thing as one mod, its addictive!
on a small budget you could get a new shifter (yea the stock one does suck)..you could get rid of the amber in the headlights which everyone hates...you could get rid of the ugly carpet panels on the doors and on the back (behind the seats)...could could get a black and white crest if the gold is ugly with ur colored boxster (the gold was so ugly with my white box)...you could paint the console...etc...theres a ton of stuff to do that'll make it look a lot nicer with a small cost..
on the more costly side you can go an engine swap, get lits, new rims/tires, lower it...etc.