By new do you mean beginner student? Unless you have unlimited disposable income, my recommendation would be to not buy a costume, but rather to spend your money on music, performance videos to study (so you can learn what the dance is supposed to look like), and classes/workshops/private lessons.
For classes, you just need a unitard or yoga pants + tank top, and something (anything) to tie at your hips so you can more easily see and feel hip movements. It should be stretchy and comfortable, and form-fitting enough so that your teacher can see/correct your movements and posture.
I agree with Mouse. I have weekly classes and am doing a workshop series at the same time now, so two different teachers. The first doesn't mind if we wear a skirt and she does like us to wear something at our hips.
The workshop teacher wants us to wear pants during warm up and skirts during dancing and it depends on the style what kind of hip scarf she wants us to wear.
goodness, I wouldn't have thought people would be that particular about it (especially early on)...the two teachers I've had, had suggestions on the type of clothing to wear and not to wear but never mentioned any kind of preference and it is up to us if we wear a hip scarf at all.
Sorry, I should have mentioned that the workshops I'm attending are for students that have at least one year of dancing experience, so we're studying the dance styles a bit more in depth.