to wear suit. skirt is always safe. you never know how conservative the interviewers are. many american males' mind set are still in 50 years ago. as long as the outfit/makeup looks good on/fit you, the price can be as cheap as you like. however, spend the most money on a good bag. it worth it.
if you haven't go to Liu Xing Shi Shang forum, please do. they're all expert can make you an expert too.
good luck.