I am considering doing a physical job hunt sometime today (Saturday, 6/11/16), and I am wondering if maybe I need to up my game in terms of my looks? And being as I have no real experience or marketable job skills, how should I sell my self?
Relax. 98% of what an employer cares about is whether you can do the job well. Going in grungy might cost you the job, but going in dressed as you would for dealing with any other adult -- not high fashion, but looking clean, non-challenging, and respectable -- is really all that's needed unless you are trying for a job in an extremely high-fashion place.
Basically, just go in clothes that don't force then to notice the clothes, and you'll be fine. No evening gowns, no rude t-shirts, no torn jeans unless that's the style they sell. Present yourself as the kind of store employee you would be comfortable asking advice from. That really is most of what they are looking for.
As a teenager you need to worry about people taking you seriously. Dress "sensibly" nothing over the top, you don't need lots of make up etc. Try not to wear tennis shoes or exercise clothes. If it's notAbercrombie & Fitch or whatever then how you look will not be the most important thing.
You will look professional and serious about it than if you bring around copies of your CV printed out. (Very old school). Have a firm handshake and make eye contact. Best of luck.
I don't think your physical appearance (how your face/body looks) is hugely important. No one expects teenagers to be great beauties, and if they do it might be better not applying for those places.
As long as you are wearing clothes and makeup that would be appropriate for the workplace you are applying for that is what is most important.
It might be a good idea to skip the dangly earrings or go for something smaller.
As @user26491 mentions a professional manner will is important.