What have you got in your cupboards / fridge?
What cooking methods do you use?
Here's an energy guide to different cooking methods https://www.bbcgoodfood.com/howto/your-guide-to-energy-efficient-cooking
Potatoes are cheap to buy but if you are baking them in the oven you are using a lot of fuel, particularly if you are not cooking something else with it.
Do you eat eggs and dairy?
IMHO a cheese sauce can make any veg in to a meal.
Tinned foods are already cooked so you don't need to cook them, just reheat.
Aduki bean burgers, a tin or two (depending on the size of your family) of aduki beans , mash half then mix the mashed and unmashed together, add seasoning and form into patties, fry or bake.
Spaghetti with lemon, zest and juice of a lemon (or bottled juice) black pepper and cooked spaghetti.
Beans on toast, add cheese if you like.
Pancakes / Yorkshire puddings can be filled with veg and savory sauces.
Scrambled eggs, on toast or with sliced tomatoes.
Soups / curries.
Bubble and squeak.
Try to plan for more than one meal, I eat meat so bad example but I will cook a chicken in the slow cooker, the following day I will take the meat of the carcass and do something with that or freeze it, the chicken carcass then goes back in to the slow cooker to make stock.
So if you do baked potatoes, cook extra potatoes, then the following day you can take the left over potatoes out of their skin, mix with flour and make gnocchi. If you have any potatoes left then make bubble and squeak.
Rice and cous cous can be used to fill any stuffed veg, maybe peppers, tomatoes and squash.
If you are cooking rice, cook extra and make fried rice the next day.