What should/shouldn't every 17 yr old girl have in her closet?

I'm looking for answers from both guys and girls on this. What are some types of clothing that every 17 yr old girl should and should not have in her closet? I've been told that every 17 yr old girl NEEDS to have a little black dress and one favorite pair of jeans. But I don't quite know what the meant by a little black dress. Should it be simple or extravagant? I have simple taste, so I'm uming that dress should be the same. I just don't know what looks good on me. My size is 36-25-34. Please help me!!! Thanks :)