If you choose to wear heels, remember to take a pair of flat shoes (pretty sandals, ballerinas ...) to still be able to make the case a horrible sore foot occurs.
Unless the dresscode so states (eg Wedding Solange Knowles, all in white) avoid all white outfits (one for all year to wear so let the spotlight from the bride is his day she shares with us).
Choose your outfit making you happy, an outfit that you will be eager to wear and that you like particularly. Because it's really unpleasant to dress in which you feel like disguised. Anyway, avoid in all circumstances to wear clothes in which one does not feel comfortable. Being nice does not mean being uncomfortable absolutely the contrary.
If you like sophisticated dresses, many women and colorful, I discovered not long ago this site: <a href="http://www.okdress.co.uk/evening-formal-dresses/" target="_blank">Okdress</a>is a site where you can find wedding dresses, cocktails, bridesmaids' honor ... I have not tested it but I found that some dresses were at attractive prices especially wedding dresses.