OK, here's some stuff. Keep in mind we lean strongly towards low-carb/paleo/grain-free diets.
First - the best most cost effective cut of meat to fill up hungry hard working bodies is probably the whole pork shoulder. Our Safeway carries it pretty regularly at 1.79 to 1.99 lb, and theirs doesn't have the same schmutz "for flavor and enhanced juiciness" added like what I see at WalMart. We can our own salsas, so this is on the cheap side too:
Brown your shoulder - or not. Put in crock pot with a quart of salsa. Run on low for a long while. Minimum, and this is once the salsa is bubbling, go 20 minutes per pound. Longer won't hurt it. Pull it to pieces when done, salt to taste if needed, serve with, oh, beans, or rice, or both, or salad, or if you can eat grains wrap it in warm, soft corn tortillas with the condiments of your choice. We use tons of salad, probably go through more than half a dozen heads of lettuce a week.
You can also roast it, covered at around 325*F, 20 minutes per pound, until the last 30 to 45 minutes for amazingly rich carnitas. I season that with garlic, cumin, salt, black pepper.
Curries. They don't have to be hot, or weird. Think of something like a fricasee of chicken, but use coconut milk and curry powder instead of the standard fricasee treatment of cream and bland spices. Coconut milk is an amazing rich, creamy addition to nearly anything. If you want to make a goulash or paprikash for example, but you're dairy sensitive, try a can of coconut milk. I recommend the Thai Kitchen brand, it's usually as solid as sour cream at a cool room temperature.
Instead of rice, we usually use cauliflower, riced in a food processor, then saute'd with a lightly browned diced onion until barely tender.
Bacon! We rarely buy sliced bacon anymore, our WalMart carries the Daily's 3 lb bricks of "ends & pieces." They work out to less than $2 a pound, and the neat thing is at that price? You can grind a pound and add it to your ground meat of whatever variety for meat loaf, meat balls, etc. Today for dinner the RN made baked catfish filets (50% off at Safeway!) with bacon on top, and "Broccoli Crack." seriously, google that recipe. There are a few variations, but the common ingredients are raw broccoli, salt, olive oil. You don't need to get fancy - canola would probably work. Heck, bacon grease would probably work.
We rarely use potatoes. Too much of that starch all at once and we're all snarly and grumpy an hour later. So we will dice a small amount now and then into soups and stews. Usually with carrots, parsnips, or any other rooty goodness that's not stupid expensive.
Oh! My special thing, that makes kids eat cooked carrots until they're too full for anything else.
Slice carrots into french-fry sort of sticks. Toss with your favorite cooking oil (for this, since it's mostly kiddos eating it, I use bacon grease or our own rendered lard - which by the way if it's from local non-industrial pigs is one of your best sources of Vitamin D.)
Then toss the oiled carrots with:
cinnamon
nutmeg
salt
SMALL amount of powdered ginger
LESS SMALL but still not a lot, amount of mild curry powder
Put in skillet. Cook on medium heat, covered until the carrots are tender, then turn up the heat, uncover and give 'em a good browning. You don't need a lot of oil, and it brings out the sweetness - about the only kids I can think of who wouldn't like it are the kind who can't eat anything that isn't sugared up.
Beer can chicken. You can use the blandest, cheapest chicken around and it'll still be pretty good. Read up on how to do beer can chicken - what I do is pour a little beer into the baking pan, then add about half a dozen garlic cloves to the beer before mounting the chicken for its final flight. At that point you could probably just give the whole thing to your hungry teen and say "toss the bones into the crockpot when you're done." Because we do make stock, we do. Lots. And it gets used too.
Y'all already know I make my own mayo. Now, for eggs - ok, we get a lot of our own but it's never enough. When you buy eggs, if you mostly make scrambles or use 'em for ingredients otherwise, consider finding who around you sells jumbo eggs. Compare prices. Our general store sells the jumbos at 1.99 a dozen, which is frequently cheaper per piece than the large or extra large at the regular supermarkets. I've found that often jumbos are same price or cheaper than the more popular large/extra large. And it's simple in our house - half a cup of beaten egg is a serving of scrambled eggs. The size the egg was before I cracked it is less important than how much egg in ounces I'm cooking. And eggs are an awesome cheap and useful source of protein!
For beef, we try to catch primal cuts on sale or clearance. Roast, or slice thin for steak, but note - even though brisket is often cheap, it also shrinks - sometimes as much as 1/3. Sliced shanks, if you can get them reasonably priced, are a slow-cooked indulgence with lots of fat and collagen to fuel growing bodies. If you favor steak, watch out for well-marbled chuck! If you catch the right piece at the right time, especially the cut closer to the ribs sometimes called "Market Steaks," high speed high heat and medium rare in the center gives you a real treat.
Tilapia can be seasoned up and oiled up, but I don't favor it as it's pretty dry. Best to cut it into scallop-sized chunks, wrap in half-strips of bacon and bake at 425* until done, then serve on a salad. Did I mention we eat a lot of salad? Even the 2 year old, she loves her raw greens and sprouts.
Did I leave anything out? I'm guessing y'all already know how to do your own starches, we don't so I don't have any suggestions there.
And we don't do much casseroles, but sometimes a Spanish Tortilla (see eggs above) or crustless Quiche.