Whatever fruit and veg are on the super 6 offers, get those for the week. So Aldi in Ireland this week has peaches, potatoes, carrot/parsnip mix, mangetout, grapefruit and apples, while Lidl had romaine lettuce, plums and corn on the cob the first half of the week with broccoli, onions and sweet potatoes for the second half.
Eggs are very versatile - a Spanish omlette using up small bits of veg and leftovers, with some cheese, is a decent dinner on warm evenings.
Lidl's double packs of bacon lardons are very versatile too - into a plain tomato sauce with pasta; bake with baby potatoes, tomato and chilli sauce (and chorizo); with a baked potato and some grated cheese; into a quiche with some onion or leeks; make a carbonara by frying lardons and an onion, using an egg and some cream for the sauce with some pasta; add to scrambled eggs or Spanish omlette; etc. If you are frying them to cook, use a dry pan as the heat will render out the bacon fat itself as a cooking fat so you don't need extra oil.
Make 1 big batch of spaghetti bolognaise sauce and freeze it in portions to use maybe once a week or fortnight. If doing a big batch, use less mince meat, and add grated carrots, finely chopped mushrooms, courgette, maybe some lentils or butternut squash etc, to bulk it out. I tend to do a batch using about 700g mince, 3/4 carrots, a whole courgette, good handful of mushrooms, maybe half a red pepper - and I chop all those very finely in the mini food processor. I tend to get roughly 3-4 meals for our family of 3 from that (DD11). You can also use some of that sauce to make a lasagna, to change it up one day - just drain off as much liquid as possible.
Other options for bulk dishes would be:
Shepherd's pie - adding grated carrot, grated courgette and peas (lentils also good here) to the mince.
Smoked fish and broccoli pie - poach the fish in milk to cook it and use that milk to make a white sauce, chop broc into florets, flake the fish, put both in ovenproof dish and cover with white sauce, top with mashed potato and a scattering of breadcrumbs and grated (strong) cheddar for a crispy top.
Beef or lamb curry using more stewing cuts of meat - needing long slow cooking and including some veg like butternut squash, aubergine, cauliflower, tomatoes, chickpeas etc in big chunks.
Do one of the famous MN Chickens! Often larger chickens are cheaper by weight than smaller ones so buy the one that works out cheapest per kg. (Perhaps buy 2 to cook at the same time). Roast or pot roast or slow cook on day 1 and have a roast dinner. Take the rest of the meat off the bones. Make stock with the bones and the peelings of the veg you used for dinner (carrots, onions, celery heads etc are all great for this as long as they were clean) and a few herbs if you have them (fresh or dried are fine). Make a curry or a stir fry with some leftovers next day, which can be great to use up small bits of different types of veg. Use the stock for soup or base of sauces - can be frozen. Freeze any more leftover chicken in portions suitable for your uses. Handy for loads of different easy meals like quesidillas or fajitas, adding a handful to a Spanish omlette or quiche, sandwiches, stir fry (with noodles or rice), or chicken and mushrooms in a creamy sauce (use the stock) with pasta/rice/mash.
You can do similar with a large joint of bacon - nice dinner, bits for macaroni cheese (I add loads of veg and bacon to mine) and any leftovers can be frozen to make pasta bake another night, sandwich filling, fry slices to serve with a fried egg and chips/boiled potato. If it's not too salty (and I haven't cooked cabbage in it!), I sometimes use the cooking water to make "ham and pea soup" by just adding frozen peas after I've taken out the bacon, and then blitzing in the food processor.
Use any local greengrocer or butcher etc for seasonal ingredients (tend to be cheaper) or less popular cuts of meat.
If you get a big sack of potatoes rather than smaller bags, they are generally cheaper overall (price per kg is what you need to check). Things like baked potatoes, using leftover mash fried up with an onion as hash, or reheated in the oven with milk, onion and peas if doing an oven dinner, etc. Make your own potato wedges and chips.
A bag of oats is also great - for breakfast porridge or smoothies, to make flapjacks for work lunch and home treats, and to bulk out things like shepherd's pie meat mix.
For work lunches, if something more than a sandwich and fruit is needed, get the bulk packs of chocolate bars - they are a bit cheaper (although often smaller) but they will give enough of a treat to entice you not to run to the shops and spend loads. They're bigger than funsize, but slightly smaller than single bars at the till - which is also healthier for you, but should be enough to sustain.
We don't have pets, but DMIL gets the Aldi tins for her dog and they are great, and only 29c each.
Can you bake? As a way to reduce the amount of bread you buy, and treats (buns, cakes, cookies etc)? Wraps rather than bread could also be good for some lunches, or leftovers from the previous day's dinner to heat in a microwave if you have access. Soup in a flask. etc