So, many people out there (including myself) are scared to push the fashion envelope. Here is a good tip for those who want to go outside of their comfort zone, but are scared.
Find an event where the fashion rule is "Anything Goes". I think of anime conventions (or other conventions where people cosplay as something). Put together a few outfits that you have never created before. Some people even go so far as to change what they wear throughout the day, so don't be scared of having too many outfits. If you are having trouble with this part (or if you only own jeans and t-shirts), borrow a friend. Borrow their opinion, their clothes (with permission), whatever. This may be a good time to get some new items. An easy way to put together a new outfit is:
Most people have those kinds of items in their wardrobe, so it is an inexpensive way to put together a new look.
If your problem is in body issues (you may feel like you are "chubby" or "fat", but that is no reason you can't dress how you want), here are some pictures of people who put caution to the wind and went for a more risque look.
Felicia from Darkstalkers
Naga from SlayersJust be sure that if you decide to dress in a costume, it is clean, and you don't come off as creepy. The following are examples of what NOT to look like
I hope this helps. If you have any questions, feel free to e-mail me here!