Looks as if almost everyone starts out with basic things such as HID's, intakes, and exhausts. After that it basically splits up with tuning, wheels/suspension work, bigger turbos, and all that good stuff. IMO, most common mods would be HID's, intake, exhaust, BOV kits, suspension work: wheels, springs, coilovers, and cosmetics: tinted windows, vinyl roof cover, carbon fiber hoods/trunks, lip kits, fog covers. A good idea would be to go to the media section, take a look a members cars and get a feel for what you like and dislike and go from there. Most members have their list of mods in their signature also.