First of all; congratulations on your cruise.
The truth is that very few people actually get seasick on most of today's cruise ships. If you do not get motion sickness riding in a car or in a small boat it is highly unlikely you will get sick on a cruise ship. My wife is quite susceptible to motion sickness and she has never had a problem on the ship. She used the patch on our first couple of cruises but when she left the patch on for the full seven days she realized that it was more of a placebo effect.
She hasn't worn one in years.
Having said that: There are a number of "preventatives" that will help in not becoming seasick. The best is Meclizine (brand name Bonine) that is non-drowsy for most people and effectively prevents motion sickness in most people. It is available in almost any drug store, Wal-Mart or Target type of store. If you ask for Meclizine, directly from the pharmacist, it is very inexpensive and non-prescription.
I emphasize "prevent" because almost all of the motion sickness medications such as "The Patch" (scopolamine and only available with a prescription), Meclizine, Dramamine and Gravol are not effective once you become sick. You must begin taking it before you become ill. The only non-prescription treatment that has been medically tested to relieve the nausea of motion sickness is "ginger".
Some people recommend the accu-pressure wrist bands but I have seen no clinical evidence of their effectiveness.
Take care and don't become overly worried about motion sickness.