I have never been on a cruise. If i did one, I'd do an Alaskan one. But I'm so afraid of running up the on-board bill that i would be afraid to go on a cruise.
I don't think of you as a shopper so I don't think that would happen. The salon is expensive, massages & hair styling, etc. I think the biggest onboard expense can be drinks and the extra restaurants that charge. Alaska is a shorter cruise so maybe one extra restaurant as a treat and the rest is included. You can buy a drink package but we don't drink enough soda to make it worth the price and since I am fussy, the alcohol options are not what I want. We only order one drink a day. You can figure out what the cost might be before booking a trip. If you like wine, instead of ordering by the glass there is usually an option to purchase a bottle and then request it wherever you are dining.
The big extra expense is the tours. For Alaska you would want to go on at least one hike. Even then you could just stay in the towns and save money.
If I could say any cruise it would be Alaska.