Maybe appearing in society for first time is not so such as it was in the past. Never the less it's still part of future memories and present delights. A girl must have in mind something not so flashy, not so loud. Go for the classic and never be mistake.
Finding an appropriate dress for a debut depends on if you are the debutante or a guest at the party. Generally, young debutantes wear ballroom or prom-style dresses. I would recommend buying one of the many magazines for debutantes or quinceaneras to find out about the latest styles.
A dress out to a little above your knee in a color that flatters your hair and eye color. I wear blue usually because it compliments my blue eyes and brown hair. A nice shrug to go with it would be nice,too.