you have not be concerned about the dress code.
My husband took 2 nice blazers on the 14 night cruise with some nice ties. And only on formal evenings he weared the blazers. On the other night he weared a nice shirt, somtimes combined with a tie or a vest.
I had some elegant evening outfits, but no gowns and no tuxedos. Some people love to wear it, but it is not a problem if you don`t do.
Hey, woman like to dress up a little bit elegant in the evenings, but a nice blouse or shirt can be perfect too.
I think with a tip, you canīt get an upgrade. But sometimes, when the ship is not booke out, you can change the cabin, when you are not satisfied. I arranged that for some german passengers, they had problems with their cabins.
So, ask if you have more questions. But doīt forget I am german, sometimes making mistakes in your language. (Love Newfoundland, have been there with the Norwegian Sun on an Indian Summer Tour).