Quinceanera Etiquette

I`m attending the Quinceanera of my fiance`s neice in two weeks. I`m not Catholic or Hispanic, so this tradition isn`t part of my heritage. As a result, I don`t know all that much about how they *really* are these days. I haven`t attended one in over 15 years.

I would like to know what the appropriate attire would be. I have a black suit that hints at a casual, feminine version of a tuxedo, but I don`t know if that`s acceptable. Also, is it appropriate for me to give her a gift? If so, what would a fringe almost-relative like myself give to her?

She`s a wonderful girl and I would hate to embarrass myself or my fiance by not being prepared.

Thanks in advance!