with eggs and cheese you can make a cheese omelette, do you know how to make one? You can add chopped red pepper as well for extra nutrition, add it right at the end so it stays firm. None of those ingredients go off quickly.
roasting a chicken is easy, just put a lemon inside it, drizzle some oil over it (or put some slices of bacon over its back or mix some butter with herbs and stick it under the skin) and roast it for an hour or so, until the juices from the thigh run clear, no red liquid.
you can cook almost any fish in a foil pouch with some olive oil and lemon slices, maybe a splash of white wine
noodles and stir fry veg don't take long, sesame oil is lovely on noodles, or soy sauce
potatoes with their skins on are healthy, roast with a little olive oil and salt
eggs can be scrambled, boiled or made into an omelette and keep for a while
salads are great in this weather, although lettuce wilts fairly quickly but I add kidney beans, red pepper, capers, anchovies and hard boiled eggs to mine. You can use balsamic vinegar as a dressing
So for that lot you'd buy
eggs
red pepper
a chicken
potatoes
butter
lemons
some fish portions (not the crap with sauces, pure unadulterated fish)
olive oil
cheese
veg for stir frying
noodles
soy sauce
I'd also add
apples
strawbs/cherries/whatever's in season
whatever veg you think you might like. We can tell you how to cook them!