Big ol' fanfic writer here.
How do you get reviews on FFnet?
Read other people's fics and review them. But please,
please, do NOT 'emotionally blackmail' someone into reviewing your work just because you reviewed theirs. Also, find LiveJournal communities that play in your fandom's sandbox and try to join in writing fests/competitions. Post to other fanfic archives beside FFnet, too. For instance, give AO3 (Archive Of Our Own) a go.
What really helps a lot, though, is playing in a larger fandom first. Larger fandoms: Supernatural, Harry Potter, Naruto, Twilight, Pirates of the Caribbean. Larger fandoms means more readers, means more eyes on your stories, means more reviews. Also, also, if after getting your feet wet you enjoy the experience, look around for a beta-reader. Although FFnet readers have high tolerance levels, there are going to be the ones who despise unbetaed works and will tell you (quite rudely) what they think about your story.
The Devil Wears Prada isn't a very huge fandom - if it exists at all. But googling 'devil wears prada fanfiction' wouldn't hurt.