Don't want to sound smug but my kids eat really well on a very low (temporarily) income. We're lucky we already have everything in place to make this happen (car to travel to supermarket, huge chest freezer, two slow cookers, cheap electric and has tariff etc - most people in food poverty are not this lucky.
I shop at Aldi, Lidl, Asda, Tesco and our local market. I time going each place to get the best deals. I got a whole enormous salmon for £3 in Asda last week (went at 8.30 when bargains good), filleted it after watching YouTube video and there were 16 good sized fillets. Aldi reduce their stuff by a whopping 50% the day before it's got to be used - hence a freezer full of chicken portions, good quality mince, sausages etc.
I buy lots of pork - leg or shoulder often £3ish a kilo. After a roast there is so much meat left to make hotpots etc in my slow cooker.
I bulk buy spuds, pasta and rice in huge bags so it's cheaper. I buy veg frozen and tart it up with spice to make it tasty
I'm also a fairly good cook, and it helps that I can look at what there is and make it taste good rather than have to buy to a recipe (like DH!)
Again, I'm lucky - all this is dependent on my existent infrastructure, and the fact that for us this is a cash flow issue rather than long term grinding poverty.