1) Nomi's first superhero or super villain costume (depending on your perspective) was not technically a costume. As essentially a refugee/runaway, she did not have access to create such an outfit and wore plain clothes. She wore a purple hoodie, pink miniskirt, beige tights and blue sneakers. Nomi was wearing these clothes for the majority of her appearances, including when she was in combat.
2) Nomi's second look was even more understated than her first featuring a long, gold jumper, gray pants and bright blue shoes. Despite fighting alongside the X-Men now as a junior member, she did not opt for a more military style uniform as did her compatriots. Again, this may have been as the result of practical restraints. As Nomi was much younger than her teammates, they may not have had her size for military garb.
3) Following her brainwashing by Miss Sinister, Nomi wore her first real costume. It was a body suit and looked very similar to a traditional wet suit with a zip down the center. The color scheme was purple and gray and it was a generic look for all members of Nomi's team. The sleeves stopped just below the elbow and she had gray gloves and purple metallic boots.