1) Nate’s first costume were the clothes he regularly wore back in the AoA, a blue form-fitting bodysuit with yellow trimming and belt and yellow stripes. The ensemble was completed by a matching short jacket with the same color scheme. Nate clung to that outfit pretty long, even after he’d crossed realities and the odd look emphasized his “alien“ nature. [X-Man #1]
2) With time, Nate more and more wore ordinary street clothes that were typical of his age; Jeans and T-shirts. Sometimes, he’d wear shirts with an X-Pattern. For a time, he wore a fishnet shirt with leather pants and a jacket on top of it [X-Man #26-28]. In battle with Holocaust, he manifested some form of psychic armor [X-Man #44] and once enraged he transformed his street clothes to a black and white X-suit [X-Man #47], but none of these became a permanent look.
3) After a visit with his sort-of-parents, Cyclops and Phoenix, Cyclops gave Nate one of his old X-Factor uniforms to wear, a blue-white suit with a prominent white X. Only shortly afterwards, though, it was slightly modified, the white elements recolored yellow. [X-Man #55]
4 When he became a shaman, Nate only wore a pair of grey-black pants and a leather coat, but nothing underneath, neither shirt, nor shoes. This showed how far he had moved away from human concerns or needs. The black x-shaped tattoo he sported on his chest wasn’t for show - it was a genetic brand - passed on to him from an alternate self - that prevented his powers from killing him as they had threatened to do from the start. [X-Man #63]
5) Upon resurrecting, Nate wore a combination of his original costume and his shaman look, a bright blue and yellow x-adorned robe over nothing but a grey-blue pair of pants. [Dark X-Men #2]
-)Upon officially joining the X-Men, Nate returned to wearing just a long leather coat and jeans. [New Mutants (3rd series) #29]