I prefer a necktie on men, as the bowtie looks silly when it gets uneven, and I think it looks most uncomfortable. Not that way it appears on a necktie, or its just my preference. I think the gray shirt, with a black tie, and silver/purple tie clasp (found as a birthstone at a jewelry store), would be the thing.
wear a bow tie - it's cool! choose a color to compliment the shirt and vest, darker or lighter shade of the same color as the shirt for example- get a self tie variety and practice how to tie it before the big night!
bowtie
For prom I would say Bowtie, probably black with your outfit, because it matches the vest. Or just go to the shop and look around, because you might find a patterned one that works really well.
If you are not wearing a tux, a regular tie looks more dressy and sophisticated than a bow tie. A tie with purple, gray and black in it would work. Actual color or combo of colors depends on whether you want the tie to contrast or blend in with the shirt and vest.
A necktie. A bow tie is reserved for when you wear a tux.
