Typically you would get invited to the ceremony and then later on to the reception. In which case you definitely want something that's versatile enough for the day time that can also transition into the evening. You don't exactly want to stand out too much. Patterns or floral prints should be save for an outdoor wedding. Depending on the location, you can even wear a more formal attire as if you were going to a nice banquet. :)
I personally don't like to wear something that's too on trend because 4 out of 5 other girls will probably have the same style or same color as you.. worse case.. the same dress!
Something like this would be a great dress for day and night.
|From Daily Look|