Halloween/Birthday Party Themes Costume and Ideas?

So my birthday is on Halloween and I’m turning 20 this year so I wanted to do something special.

I’m not sure what kind of theme I should go with. I’ve had a lot of ideas thrown at me by some of my friends. Rocky Horror Picture Show, Random Weird stuff everywhere (Not sure that’s a theme) and there’s been a few others that I can’ remember right now.

Anyways, I haven’t really liked any of the ideas my friends have given me so I need some help. Please keep in mind that I’m a college student and money is low with me. So there’s not a lot of stuff I can buy.

Also, I’m giving the option of letting my guests dress up if they wish. I was wondering if anyone had any cheap or homemade costume ideas floating around for me?

Halloween Tights – Fancy Dress Ideas UK

Jersey Shore theme party costume idea for a skinny guy?

Any ideas?