I’ve mostly been a single mum on a very tight budget my tips are:
Make sauces from scratch - most are really easy once you know how. The easiest to start off with are tomato based sauces - pasta, chilli, Bolognese. Then roux and you may feel brave enough to try more advanced ones
Peasant dishes - these are naturally cheap of course - stovies, ratatouille, dahl, pasta with simple butter or oil and herbs to flavour, stews, soups, rice dishes...
Mince with everything - chilli, shepherds pie etc
I discovered during lockdown it’s SUPER easy and quick to make your own flatbreads. Just plain yoghurt and flour!
Follow the “old tricks” of our foremothers - soup starter, bread and butter on the side and plenty to drink (water or milk ideally but a large pot of tea is also easy and cheap) to fill up on.
Cheap carbs as the base for most meals, my Dd can’t eat potatoes so I’ve become accustomed over the years to using different carbs, mainly pasta, cous cous (I buy a kilo at a go and store in a plastic tub) and rice - there’s no rule says you HAVE to have potatoes with a stew carbs are neutral flavour wise so will go with anything.
Eggs 100 ways - I recently rediscovered baked eggs which are so easy. There's also omelette, frittata, shakahuka...
Cheaper fruit for snacks/dessert - forgo the berries and melon for apples, bananas, oranges etc shop seasonally
Meal plan so you’re buying stuff that’s suitable in several of the dishes you like to make, eg I’ll use peppers in pasta, casseroles and stir fries too. Same applies to herbs and spices choose versatile ones
Batch cook and then on days you don’t feel like cooking from scratch you have home cooked “ready meals” that just need reheated.
Keep an eye out for GENUINE bargains when shopping BUT don’t buy things you know deep down you won’t use.
Non food but could be applied to non perishable food - I never pay full price for my preferred original fairy liquid I stock up whenever it’s on a special offer. I’ve just done the same with baked beans recently - they were on a “4 for” which really is too many for me but they’re tins! They’ll last! So I’ve stocked up and now they’re not on offer any more (for a while at least these things tend to be cyclical) I don’t need to buy for a while.