Don’t sweat this. Wear something simple, casual, comfortable. Should be neat, not sloppy. With comfortable shoes. When DD arrived, she wore khakis and a polo shirt and sneakers. Fit right in.
More importantly, pack light. She had a soft bag that she could easily shoulder. When she and several others were speed-marched from the check-in table to the barracks, I felt badly for the guy hauling the huge suitcase and the girl toting the massive duffel.