I wish I could help you out on the ship but I'll leave that to some of the other more experienced cruisers.
Your other expenses could come from things you buy on the ship, pictures purchase, buying pop (don't know if this is incuded but on Carnival its not) and gambling. All of those things can add up if you choose to purchase them. Speciallty coffees can also cost you extra. Bottled water.. that will absolutely cost you. Your shore excursions all cost extra and they are not cheap so check the price sheet before you sign up. The extras can add up quickly.