I felt most comfortable in dress pants, nice blouse, and a blazer. That's what most of the other girls at my interview were wearing too. It doesn't have to be boring or expensive though, I think the most important thing (besides looking professional, of course lol) is that you are comfortable and feel like yourself. If you do choose a skirt though, I would actually encourage wearing tights, it finishes the outfit in my opinion, even if they're nude/sheer.