Along with what everyone else said, there are no "rules" when it comes to ordering. With the DDP you get an entree, a dessert, and a beverage per TS meal
On a cruise, get what ever you want. The apps look good to you - order 3 or 4 of them. Entree did not fill you up - get a second. As long as you are not insane about it, they will be more than happy to accommodate you. Ask nicely, and try not to waste food. If there is something that interests you, but you don't know if you would like it, ask for a small portion, don't just order a full serving. Also, try not to camp out in the dining room if you have first seating, they do have to prep for the second wave.
There is no lack of included food on a cruise.
-dave