Aftermarket installations

This is my first time doing a forum. I just recently got a 2000 Celica GT and was wondering what i can do to fix it up. confused
I was looking into buying rims for it i found 18"x 7.5 rims and do not know what tire size to go with.
i was also wondering of there is a dual exhaust system some one recommends that sounds deep like the GTR's do when they take off or like the old muscle cars do i really enjoy that sound.
if anybody could help me this is my first car and i want to make it look and sound good nothing like those crappy Honda's that take of and sound like they're going far but are just moving 2 ft from where they started.