Hi MCD,
Your concerns about deciding how you are going to handle you expenses is the same as most cruisers have. Most cruise lines recommend tipping for your cabin attendent and waiters at about $10 per day per person. This can be paid in cash at the end of your cruise or in some cases charged to your sail and sign card. Room service is usually performed by other staff members who are usually tipped about 1 or 2 dollars per event. All other purchases on board are made with your sign and sail card and, when appropriate, a 15% tip will be added to the purchase price. On board purchases might include sodas at dinner, bar purchases, bingo cards, spa services, specialty coffees or ice cream, photographs, art auction purchases or port excursions. All of these items are optional and can must be charged to your on board account. Port excursion prices do not cover gratuities so you might want to allocate a few dollars for each planned excursion. Since you are on the Europe board you will have to figure out what foriegn currency spending you will be doing, but souveniers can be purchased on your credit cards. Gambling on board can be accomplished with cash or most ships have ATM facilities. We have found it is always a good idea to carry some small bills to tip for baggage handling, etc. Really not as confusing as this may sound, but this should pretty well cover what you will be spending, and prevent unexpected surprises.
Hope this helps,
Peter