How to dress like Sierra Kusterbeck?

I've got edgy hair, but now I just need to learn how to dress more punk rock/edgier/darker. Just a little bit, I don't need to go all out. I just joined a rock band so I want to mix up my image a little bit. I'm going for Sierra Kusterbeck's look (lead singer of Versa Emerge) or some Demi Lovato. Maybe even some Miley Cyrus mixed in with Wendy something (lead singer of Fireflight). I know it's costly to dress cute, but there's gotta be cheap places to go to get awesome clothes. Thanks!