We're trying to economise a little as well and also get back to healthier eating (we've not been very successful at that the past 3/4 years for various reasons - but have been much better in the past). Also in Ireland, so more expensive food, and as well as DH and I having very busy FT jobs, DD has some food issues (SN related) so we need to have things that she will definitely eat for school lunches and make for herself when she gets in after school (she's Y6 and gets home 4pm, we're in about 6)
I'm trying to cut back the discretionary beer, wine, treats spending.
I'm trying to get back to my batch cooking and freezing ways.
I'm getting better at shopping the offers of things we would use anyway and either swopping out from the meal plan or keeping for the planned use next week (freezing in between, or just keeping in cupboards).
I'm also trying to get back to growing some veg in my (spare?!) time. We have the last tomatoes and some beetroot still, some handfuls of broccoli yet to come, and a couple of leeks. I need to plan better for next summer - but I do have a few bags of French beans (surprising glut) and some broad beans in the freezer from earlier.
I add loads of veg to most "sauce-y" meals, like curries, spag bol, lasagna, shepherd's pie etc. Some it's diced very finely (like 4 carrots, a courgette, a pepper and a large handful of mushrooms added after the meat is browned before the tinned tomatoes to lasagna) while others it's chunky (like quartered tomatoes in a rogan josh, or butternut squash, cauliflower and beans into a different chicken curry), or mixed (whizzed carrots but whole peas in a shepherd's pie).
I also like meals where you can add a lot of small bits of veg, generally stir fries but I use that principal for lots of pasta dishes too. So my "mac'n'cheese" has bacon (leftover from a joint or a pack of lidl lardons fried up and then use that flavoured fat for other frying!), onion, garlic, mushroom, peas, peppers and courgette in it. I do a very large pot of that for dinner one night, and freeze the leftovers to make a pasta bake easily another night (although fine reheated in pot/microwave next day from the fridge, it's not great just reheated in a pot from frozen, but as a pasta bake works very well after freezing). Nasi Goreng uses up cold rice (great for leftovers), a tin of tuna (I use the one in oil, and use that flavoured oil to fry things in), onion, garlic, and then a mix of whatever you have like mushrooms, peppers, courgette, peas, beans, brocolli florets, cauliflower florets, sliced brussels sprouts or shredded cabbage, sliced carrots, the inner part of broccoli stalks finely sliced (my supermarket gives them away "for rabbits") etc, with some tinned sweetcorn, a handful of frozen prawns is nice, and some mild curry powder.
So dishes like those are great to use up a small amount of something that wouldn't either be enough on its own or that is looking past its best.
I try to also make a plain tomato sauce (onion, garlic, tinned tomatoes, salt and pepper) to freeze in usable batches, and then I can transform it into Italian or Mexican or Indian very quickly by adding the spices/herbs/seasonings. As a base for meatballs, with some leftover frozen roasted medditeranean veggies with pasta, making a chicken tikka masala with leftover chicken, or a quick beef or veggie chilli.
I keep tins like tuna (in brine and in oil, for different uses), sweetcorn, tomatoes, coconut milk and some soups.
I also have some good jars for nights when I have no time or energy to cook - to prevent me getting a takeaway. Italian sauces (I generally have Sacla tomato and roasted vegetables, and tomato and chilli), Indian (Uncle Ben's mild curry, Pataks - we like about 3/4 different types, and also Pataks and M&S pastes for Korma, Tikka Masala etc).
I love a dinner of leftover mashed potato fried into a cake thing (I usually add grainy mustard and some onion), with some black pudding and a fried egg. You could have a sausage or rasher with it to make it more dinner-y, or leave it to just egg and mash.
We've started keeping a full loaf of bread in the freezer. We were buying the half loaves, as we never eat a whole loaf in a week and throw lots out (even though I try to catch it in time to make and freeze breadcrumbs, as I have loads of uses for those!). But even those were getting thrown out. Whereas 2 slices from the freezer thaws quickly for sandwiches, still makes fast toast at night for those who get the munchies, and there is far less waste!
Big joints, while expensive, can often be very worthwhile as you can get so much out of them. I did a roast lamb shoulder a couple of weeks ago, fed the family, had leftovers next day, froze a large chunk of leftovers and made a pasta with roasted veggies and lamb dinner, and the leftovers of that are tonight's pasta bake - so 4 dinners from a €12 joint. I do similar with a chicken - chicken and mushrooms in a creamy sauce (cream and white wine, or a tin of Cambell's condensed soup!) is a great way to use up leftovers and can be served with rice, mash or pasta. Thai chicken broth, chicken risotto, curries - there are loads of ways to "elasticate" your chicken.
Sweet potatoes are great and cheap. Sweet potato oven chips are great - slice into chip size, mix with some oil and seasoning and bake in a hot oven for 20 minutes or so. Or added to root veggies for a roasted root vegetables side (or main event) with a roast dinner. Or as part of a vegetable curry or vegetable chilli (I don't have a chilli recipe, but we took the Jamie Oliver Friday Night recipe for curry and its yum).