If you don't already have them then have a look at getting a slow cooker and a steamer. In a steamer you can put meat / fish wrapped in foil parcels, add potatoes and veg and you have a complete meal.
To cut down on washing up buy slow cooker liners.
Do some one dish meals in the slow cooker.
Chicken pieces or thighs, a tin of condensed mushroom soup, sliced mushrooms and green beans or leeks. Put in the slow cooker and leave. serve with potatoes or rice.
I live alone so it is far too much for me so I put the leftovers in a foil container and add a pastry lid - this goes in the freezer for a later meal.
You can roast a joint or a chicken in a slow cooker, just put it in, put the lid on and turn on. You can add seasoning or herbs if you like.
Have a look at shopping from Iceland, they do a load of things with instructions for the air fryer.
Do you have a toaster? Get some toastie bags for things like ham and cheese sandwiches. You can cook potato waffles in a toaster too.
Stuffed peppers work well in a microwave.
A PP has said cous cous, you can also make bulger wheat by just adding water.
You can 'boil' eggs in an air fryer. You can also cook them in the microwave, butter a ramekin, break an egg into the ramakin, PIERCE THE YOLK, you can add seasoning or a drop of cream or even a bit of grated cheese.
Consider buying paper plates to eat anything messy.
You can get a collapsible washing up bowl to save space in the bathroom.