It depends.
A few extra minutes when going around the supermarket to check prices can make a big difference. Whether that's considering between named brands and stores' own brands, or even just between sizes within a brand (generally, the larger size works out less per unit (kg/l/washing capsule etc), but sometime the smaller sizes are the better ones so it is useful to do a mental calculation).
If you have coupons to use on things that you would be buying anyway, then it makes sense to use those and reduce the cost. But don't use coupons on things you don't normally use unless you want to try it out once, but not just for the sake of making a saving. Or buying "3for2" offers is great on things you will use or that you can put the 3rd into longer term stores to use in the future, or will reduce the cost of a nice version of something to the same or less than the cost of 3 of the cheaper version IYKWIM (so buying 3 Sanctuary shower gels on offer could be ok if the cost of the 2 that you pay for is the same as or less than the cost of 3 of the shower gels you normally buy). So you get a nice treat but it doesn't cost you more.
But buying bags of salad on "3for2" is not so good if one and a half of those bags will end up in the bin as you can't eat that much salad so fast.
Buying "yellow stickered" food is often fine - check them carefully to see if they are still ok, and either use quickly or freeze. And don't get things you won't eat just because they are stickered - get things that you know you will use. Personally, I don't usually get berries, salad leaves, spinach, pre-chopped fruit/veg, cooked meat, liver or mince that is yellow stickered - but I will get joints of meat, chops/steaks, especially bacon, other fruit and veg that is whole and looks ok, eggs, etc, and I will very carefully examine chicken or fish to see if it is still fresh enough.
I will also make good use of things that are going past their best in my fridge - different kinds of stirfries to use up handfuls of different veg, Spanish omelettes, potato cakes with different fillings, diced mixed roasted veg, etc.
I'll spend on some things to make life easier - stretching my money as Empress refers to it. Like paying €800 per year for a car parking pass for parts of my local town - but I use it daily for my commute to the city by train, on Saturdays in another part for my Cub Scouts meetings, and Sundays in another part for organising Junior Sailing, and can use it to park for shopping in the town at times just walking further than if I'd parked in the shopping centres - so it is worth it to me.
One thing I have done to try and spend less is to take out money at the start of the week to cover incidental spending (coffees, lunches, occasional book, etc) and try to not spend more than that amount. It does help (or did, until Covid meant most places want card sales only).
And loyalty schemes in supermarkets, chemists, etc can all help - getting vouchers occasionally, and also money back based on your spending (usually vouchers to spend as cash in that shop, but Tesco ones and now SuperValu ones have booster offers alongside). But I have signed up to them all, to get all the points no matter which shop has the better offers on different weeks (although I also shop in Lidl and Aldi even though they have none, and the Asian supermarket near my office for certain things occasionally which also has none but is very cheap for spices and other items).
I also have good menders for my things - a couple of cobblers to repair heels and soles on shoes, 2 decent tailors to alter and mend clothes, and an electrical guy who is good at fixing various appliances. Buying quality items and keeping them in good repair is worth spending the money on as they generally will last a long time and cost less over that time than buying (and needing to replace) a number of cheaper items.
And while it felt like spending a lot when I was just getting married and getting our house, I bought a sewing machine and that has saved me a fortune over the years. I've made really good curtains for 2 houses (basic floor length curtains for a north facing single glazed bay window were over £400 18 years ago, I spent under £250 on fabric AND interlining (blanket type stuff for an insulating layer) and made them myself - they not only looked good but also saved our heating bills hugely before we could replace the windows), cushions and other soft furnishings to match, shopping bags and storage bins, loads of repairs, and lots of gifts for people too. And it is still going strong.