Okay, there are a few things you need to know...
1. Next time, please attach your image to the message rather than sticking it directly in the post. It is very large ^.^;;;
2. DO NOT go into a costume contest expecting to win. I'd say that even if you were a seasoned veteran. You'll only get dissapointed most of the time.
Now that THAT's over with, I have a few questions for you!
1. Are you male or female? (I'm GUESSING that you're female, but... you never know!)
2. Going with the first question, would you like to stick more to the animalistic form (the first thing that comes to mind is "Esper Terra", but many Final Fantasy summons are done in this style) with clothing "simulating" the animal bits (such as two long scarves simulating a tail) and using very animalish fabrics (furs, suedes, etc) or turn it into a more human form such as a dress (PikaBellChu's lovely pokemon gowns come to mind) or swimsuit type garment.
3. ... It's the dreaded question... What's your budget?
This should help us help you out a bit