Wardrobe really depends on the situation. I have a large one for a guy, cost of doing business I suppose.
I would think that khakis, flats and a cardigan would be fine for an interview. I would go for muted colors or the classic tan and white combo. Keep the make-up dialed back, maybe half the wing that you usually wear. Comfort is important, if you are stiff in your clothes you will appear as such to your interviewer. As far a shopping goes, after you get the job you can look at what is and isn't allowed, and tailor your wardrobe to fit. (No pun intended)
In any event, good luck and keep a ready smile, you'll be fine.