If you are bringing a couple of steamer trunks you can have as many dress suits, regular suits, sports jackets, etc. as your vanity might wish. Practically, however, all you really need is one dark suit or tuxedo for formal nights, one blazer or sports jacket (which you can wear while boarding - as the pockets are convenient for documents, etc.); for other nights, perhaps three neckties, a couple of white shirts, perhaps one blue and one striped shirt - to be able to be dressed differently for a couple of dozen nights.