The most important thing is that you're comfortable, that you feel natural, and that you're wearing something that's representative of who you are. If you're a jeans-and-t-shirt person that is ok too. If you are driving to the location, I don't recommend wearing your clothing while you drive. Arrive early enough to give yourself time to change and feel fresh. Coordination is okay, but I don't encourage matching. The outfit does not need to match that of your future spouse. if we are doing a beach photo session, bring a second outfit in case we get wet. Consider your location when you're deciding on your engagement session outfits.