If you want the soda card, and good service...pick a few bars in the ship the first day and introduce yourself and tip the bartender. They will be glad to help you when you show up with your card! If you have children on board with cards, take a minute to introduce them as well, and teach them proper manners for ordering their drink. It amazed me that children would walk up to a bar and start banging the card on the bar to get service!!!!!
We tip the waitress in the lido rest. the first day also, and they usually go out of there way to help, last time she would see me coming and have my coffee and my sons milk ready for me when I arrived! These people work for tips, they will go out of their way if they know you appreciate it. ($$)
The waiter at dinner always had milk ready for my son also, after the first night..he knew to have it there.
There is an entire string of posts in "know before you go" about getting booze on board.
Money, this depends on your gambling habit, your shopping need, and your drinking ability. Take what you can afford to spend, you will enjoy yourself at any level of spending. Our first cruise we took $500.00 the most recent we spent about $2500.00.
Both trips were great!
Have fun!