Gibraltar will accept sterling or euros and everywhere else euros will be the order of the day...as the ship is in the Med I would think Euros will be fine for tips as well ..as the crew will be able to spend it ashore or change it if they wish.
Your on-board account will be in U.S. dollars and if you don't have your tips added to the account they can be paid in Sterling, Euros or Dollars. You will not use cash on the ship so Euros will be all you should need. ... Nei.
All purchases aboard Independence will be logged to you on board account in dollars (we found this really good as you get almost 2$ to the pound) anything on shore will be in euos.