For a couple of years, I was doing the monthly grocery challenge on MSE, and that worked well to keep me on track (I had a basic budget I was trying to keep to for the year). But work blocked MSE access and I can never manage to get on at nights.
If you are into any kind of Asian food (Chinese, Indian, and Thai especially), try to find an Asian supermarket near you. The spices are really good and sold in bulk (not sackloads, but 200g-500g packs which do loads). And they do very good value larger bags of rice and noodles (up to 20kg of rice!! But I tend to stick with 5kg). They often have interesting vegetables too, and they are generally good value. I try and go about every 3-6 months to my local(ish) one, to stock up on herbs and spices, and rice etc, and then add a few fresh things while I am there.
The same with Lidl or Aldi. I like things from both, but don't get there too often. (Well, Lidl more often). So I will stock up on Lidl bacon lardons (usually have about 6-8 weeks to use them), loads of cheeses (big blocks of vintage cheddar, a couple of gorgonzolas for gorgonzola pasta, feta, parmesan etc), their beer and wine are good (we've trialled extensively to find what we like), a few packs of parma or black forest cured ham, (they've got braeseola now too, yum!!), frozen fish, frozen oven chips, individually wrapped criossants/pain au chocolats for breakfasts, loo roll, kitchen roll, cleaning things etc. And then get loads of fruit and veg, and 6 cartons of organic milk, for that week while I am there.
I do "shop the offers" on things we eat. So use the freezer wisely to stock up on some of those offers.
I do big batches of roasted veggies (1cm diced red onion, courgette, red and yellow peppers, tomatoes, garlic, mushrooms - tossed with some olive oil and seasoning, roasted for 20-30 minutes) - using some for dinner and then freezing in roughly 1 rounded cup batches. That's enough for 2 adults as a side dish another night, or for all 3 of us when added into tomato sauce with pasta - sometimes with bacon pieces, chopped sausages, diced chicken or prawns, sometimes just veggie.