I tell grandkids who go to college: if you have cooked eggs, cooked potatoes & cold rice in the refrigerator you won’t go hungry. Those are meal starters.
I cook big cuts of meat then it stretches for extra meals & I think cheaper too. 3# meatloaf to warm up & add a vegetable & salad. This week I cooked a turkey breast so it fed us 3 days, just a vary the sides but I have a husband who never complains.
One grandson & his wife both work, have a baby & live 10 miles from a grocery store, so they plan out their weekly menu & shops after work on Friday. She has a grocery store near her work but their plan eliminates stopping all the time.
Being efficient to me is is all about planning.