Of course sometimes it can be hard to choose what is the perfect dress to take with you or should you wear a traditional Tuxedo or not. But really isn't this part of the fun with dressing up for a cruise is that you are doing something that you do not normally do.
If you do not have a Tuxedo then you might want to check with the cruise line because in many cases they have rentals available for you and this makes it easier than trying to buy or rent one at the last minute or even worse forgetting all together.
It is always best to check ahead when planning a cruise and see what the requirements are for the formal evening on the cruise. In some cases the men are only required to wear a suit or just a sports jacket. Some cruises require that you have a Tuxedo and that you stay all evening in the formal attire. Make sure that you check ahead that way you are prepared no matter what the requirement is.
Remember that taking a cruise is an exciting vacation and you should enjoy yourself and if you are not the type that likes to dress up then you can always go for the buffet on the night of the formal dress up night.