I can only tell you what's worked for us.
I buy big 54lb bags of potatoes in the farm shop. Lasts me at least 3 months. £5
Rice, Tilda £1 for 1kg in homebargains. Same price as the big sacks in Tesco per kg but easier to store. Tilda rice always turns out nice.
Bread, make my own but I nagged Dh for a breadmaker years ago. He still has white sliced. The price of flours barely moved in the last 10 years compared to the price of bread.
Pasta, 20p in Aldi. I can't taste the difference.
Meat, Waitrose. They do really good offers (it was £20 off for newbies) & have a loyalty card with 20% off various items. Things you'd actually buy regularly. The discount applies when the items on offer too. I buy frozen mince, chicken breast strips, huge blocks of cheese etc. I go for cheapest per kg, usually the meat counter beef joints are cheaper than their essential beef roasting joints. Everything's portioned up & bagged for the freezer on delivery day. I've only got three drawers so I've had to learn to pack it efficiently.
Veg, frozen. Except carrots, cheaper to chop & freeze at home. I get a free times paper from the mywaitrose card for peelings.
Tea, dhs main drink. Tesco smart price. He never noticed when I stopped buying pg tips & I didn't mention it.
Cakes/sweet stuff, I bake my own using vegan recipes. It's mainly oil, ordinary milk if your not vegan, flour & sugar. Very cheap.
Things I've started cooking from scratch. Yorkshires, pate, breadcrumb stuffing, spicy lentil soup, cakes, biscuits, marrowfat peas from dried.
Cleaning materials. All Waitrose smart price. I make my own laundry detergent. Moneysaving expert reckon we're less likely to swap cleaning products than food quality which seems mad to me.
Things I still buy in Aldi. Mayo & white bread, white vinegar for laundry softener. Eggs, baked beans.
Cat food comes in the Waitrose order or if I've got enough vouchers from doing surveys I buy 96 pouch boxes off Amazon.
Musclefoods do huge meat hampers for not much money.