Comfortable safety shoes, work clothes and a good attitude.
Many work clothes may be provided by the vessel, including work shoes, but they are frequently less than comfortable. The ship's store will have all the smokes, candy and general paraphenalia that you'll need. Just bring enough to get going.
Presents for the officers? Gold and diamonds are usually acceptable, but if these are out of your price range, a ball cap from your school is always a nice touch.
Have fun! Just remember that MSC is an interesting mix of merchant marine and Navy, which may or may not be your cup of tea. There is a lot to be learned for the interested cadet, however.