When I buy the Mesa Sunrise flakes, I add a bunch of seeds, nuts, dried fruit, coconut flakes, etc. to it to try to make it more filling and nutritious. I do limit them to 1/2 cup (which they scoop themselves, heaping the measuring cup until it's about 3/4 cup) because we just cannot afford to let them eat too much of it. Then I let them have 1-2 pieces of fresh fruit to go along with it (usually choosing between bananas, apples, oranges, and pineapple slices). A lot of times we also make chocolate banana smoothies or fruit smoothies.
My kids used to feel the need to eat at least 2 sandwiches at lunch time, along with pretzels or chips, juice, and whatever else they could get their hands on. Once we went gluten free, we stopped eating sandwiches. I just can't afford to
A typical lunch in our house might be one Food for Life rice tortilla, made into a quesadilla or wrap. For quesadillas we heat up one side in a frying pan sprayed with olive oil or lightly wiped with a little Spectrum shortening. When that side is warmed up, we flip it over, add our filling to a half-circle portion of it, fold over the other half, and allow it to heat up some more. I flip it over again, just to let that side heat up a little, too, and voila! It only takes a couple of minutes, and we can really be creative with our fillings. For wraps, we just heat both sides of the open tortilla until warm and pliable. Then we put it on a plate, add our fillings, and fold or roll it into a wrap. Besides the wrap, we have another piece of fruit or some fresh veggies (maybe some carrot sticks and/or celery sticks) or salad. Sometimes we just have brown rice and beans and/or vegetables for lunch. Sometimes we'll have a couple of rice cakes with peanut butter and slices of banana. Our two boys are really starting to eat a lot because they are in their early teens and need more calories. They do eat more helpings than the rest of us because they seem to be more hungry. Usually I will let them have two quesadillas plus fruit or veggies.
My sister has perfected a recipe for GF buns that she uses in place of sliced bread. I may try that sometime. Her family loves them. She was making bread every day in her bread machine until she started making the buns. If I had a bread machine I might bake bread more often, but I don't have one.
Snacks in between meals might be hard boiled eggs with a little sea salt, fresh fruit, fresh veggies, 1/2 c. homemade snack mix, a modest handful of GF organic tortilla chips with some homemade salsa, etc. Snacks should be small, not the size of a real meal. Again, my boys get more because they need more right now.
Fruits, vegetables, beans, and rice are all filling and can be reasonably priced if you get what is in season. We try to eat more of those things and then have a small amount of the more expensive gluten free foods, instead of the other way around.
We usually have naturally gluten free meals for dinner, such as chili, beans and rice, various soups, meats with potatoes and vegetables, salads with chopped meat and lots of other toppings, etc. Sometimes we will have gluten free pasta dishes or homemade pizza.
Something I've noticed is that when we drink as much water as we're supposed to in a day, we don't seem to feel the need to eat as much. I think our bodies misinterpret thirst for hunger sometimes. I try to encourage my children to drink more water because if I don't keep on them about it, they'll drink 1-2 glasses of water a day. Since we don't drink much juice, milk, soda, or other processed drinks, 1-2 glasses of fluids per day is far below the amount that they need in order for their bodies to function properly. I know that I have the same problem myself. I'm much hungrier when I'm not drinking enough.
If you are confused about a portion size, just do a google search on portion sizes, or you can get a good visual idea right here.