Welcome to cruise-chat.
More information is needed. How long of a cruise do you think you want to do? Are you willing to fly to the port? Are you looking for a cheap getaway or something more substantive? With 5 people you are quite limited if you want one cabin. This gets into suite or family stateroom territory (more expensive), or more likely two cabins adjacent to one another. Carnival will put 5 people in one cabin on some ships, and on a limited basis. The other lines will not put 5 people in a standard cabin.
You must have some idea of where you'd like to go. If cruising from the U.S. in the winter, you have fewer choices - those being the Caribbean itineraries, Bahamas, and Mexico for the most part.