Which ship? Which restaurants?
the general answer is, You may order as many courses as you wish.
If you want an appetizer, a soup, salad, a main, and a dessert, Go for all five.
if you want just three courses, thats ok too
Since you titled your thread OBC, I am thinking that you are inquiring mostly about the extra cost specialty restaurants rather than the main dining room?
But some clarification on your question would help us give you a better answer