Well what are you looking to do with your car? Do you plan on taking it to the 1/4 mile track, auto-cross, just cruise around in? You thread title gives the impression you are just asking about exhaust. But your post makes it seem like you are curious about your first mods??
But yes, I would definitley do exhaust. Cat-back for sure. And get a aftermarket mid-pipe if you want more sound and a little bit more power. Maybe headers as well.