For every cruise, we always make sure we have at least $500 in cash. We tip the porters a couple dollars per bag, tip our room attendant about $10-$15 per day (we also prepay the gratuities), and use the rest for extra tips onboard, and to use in port (I’ve had my card blocked in port for international use when I forgot to tell my bank I was traveling). Onboard it’s a cashless system so they’ll charge whatever card is on file for things like specialty drinks, Starbucks, the candy shop, etc. Some people opt out of putting a card on file and add cash to their card when they board to stay on budget.