Mayve my approach will help you?
I already had a well stocked pantry but I've added a few more things that keep well: soups, a few tins of fruit and veg, beans, oats, crisp breads, long life milk, and a jar of hotdogs. Fruit and veg in the fridge and sitting out already would last days anyway and go first- plus whatever is in the fridge. Oh guess I'll have to eat that tub of hummus and all the cheese!
I've cooked some bacon chopped up and put it and some tortillas in the freezer. If the power goes out, bacon goes in the frozen peas for pea salad when the freezer stuff thaws and the frozen bread/ tortillas keep the soups and beans a bit better as a meal.
I reckon in a power outage situation (which is what we are most likely to have) working down the fridge items, then freezer items that can be eaten thawed and then pantry I can go at least a week especially if it's cold outside and stuff can go out in the shed. Longer if we get into some creative just eating for calories- dates, peanut butter, etc.
I won't be doing the whole camping stove thing but the South African neighbours will likely be grilling what is thawed from their freezer so maybe we will make trades!
I also restocked what I was low on- some spices, baking supplies and any hygiene items-
so that we have a starting point of not having to go out. I do need to do a little stock take and make sure we keep eating what we have and replacing it.
All in, I'd say I probably front loaded £100 ahead of what we normally buy to be stocked for the storms and in general, but other than the hotdogs, long life milk and the water, there isn't anything I wouldn't have bought and eaten anyway. My parents live in a rural area prone to flooding that blocks a few roads out so I'm kind of used to it.
My advice is to build on what you have and start small. You probably already have lots that is useful- you just need to be a bit broader in case you have no power unless you have a gas stove/ oven which we don't.
Add some batteries and a bit of cash, and call it a day!