I batch cook things like bolognaise, shepherds pie, curry, fillings for fajitas and tacos (can also be used with spicy rice), chilli, casseroles etc.
All of these are usually about 40-50% meat, the rest veg etc, so bulked out with extra veggies. I then freeze in the right portion sizes so there isn't any waste. I then serve with a carb and more veg. I buy a lot of meat on reduced stickers (Beef mince, chunks of beef, chicken breasts/thighs, etc etc), and adapt what I'm planning to make depending on what I can find. The fact that there is so much veg in the meals means that one large pack of mince makes tons of meals, same as a pack of chicken etc. I also will use one base to make different meals. E.g. the shepherds pie base can be shepherds pie, beef pasty, beef pie, served with little roast potatoes, Yorkshires and veg etc.
Lunches are either sandwiches (ham, cheese or tuna mayo) with raw veggies, or omelette/scrambled egg with toast and veggies, or ham or cheese wraps and veggies. That sort of thing. The ham is only cheap, the cheese is value, the tuna is bought on offer. Eggs are cheap but filling.
Breakfast is either cereal and fruit, toast with peanut butter or jam with fruit or sometimes banana pancakes (just egg and ripe banana mixed) with fruit on top.
My daughter eats really well. Her diet is full of all the vitamins etc that she needs, but it doesn't cost nearly as much as it would seem.