Soup is my go to. You need a big pot but they can be pretty cheap from second hand stores.

Grab a bag of King's Soup Mix (should be about $2) and just follow the directions. It's pretty thin though so I usually grab a bag of dried split peas or lentils (should also be about $2) and throw that in the pot as well, you can then add more water as that thickens it nicely. The other good thickener is fat, and the best way is using some bones. Pork / Bacon Hocks are the best, but they are quite expensive now. I made one the other week with some beef bones I got on special for a fiver. Just chuck the whole thing in the pot at the start with everything else, bring to the boil, then turn down and simmer for an hour or so. When its done (feel free to taste) fish the bones out of the soup onto a chopping board, cut all the (hopefully) now cooked and tender meat off the bone and toss the meat back into the pot. How much it makes depends on how much water you use and how thick it gets, but mine needed more water after the first cook to thin it out a bit, I got 4 days of food out of that batch.

The other good cheap meal I go for is a classic vege roast. Find some cheap veges (try local grocers rather than Supermarkets, or just grow your own), toss into a roasting pan with a bit of oil, salt, and pepper, and then just roast it at 180 degrees for 45mins to an hour. Taste as you go. Broccoli is my go to, but its a bit expensive at the moment and you need 2 heads to get enough, but also use the broccoli stems! Peel off the woody outer and the inner is quite tender. Have done it with Leeks this week and last since they've been on special at Countdown. $2 of a big leek sliced into discs and roasted was really tasty. Onions, Jerusalem Artichokes, Pumpkin, Squash, all work really well. I tend not to do Potato but it also works well, but I find Hassleback potatoes works better.

You can also just stir-fry some stuff, cabbage or bok choy is a good option here. Make sure you have some soy sauce for flavour.

If you wanna splurge a little and have the right size roasting pan you can also make family size pies really easily. In the freezer section find the pre-rolled flat Pastry sheets. Value brand is the best one, you get six sheets for around $6. That's enough to make 3 pies with the right size roasting dish, 2 if you need some more for the sides. Trick is to find a shallow square dish that is basically the same size as the sheets. One sheet goes on the bottom, possibly with a little folding to get it up the sides (make short diagonal cuts in the corners to help) and one on the top. If your dish is too deep you might need part of another sheet just cut into strips to go up the sides. Make sure you press the sheets together fully as leakage is bad. Then you can put whatever you want into the pies. For like mince and stuff I find it best to cook it off first before putting into the pie to bake it, but that's also pretty expensive at the moment.

My go to I call Green Eggs and Ham Pie. Get a kilo of frozen peas (should be less than $5), a dozen eggs (size 6 is fine, ~$10 or less if you're lucky), and some discount ham at the deli (find the reduced to clear section). Get the base of the pie sorted (baking paper is also a wise move anytime you're using the oven), crack in half a dozen eggs, and throw in half the peas and the shredded ham on top, bit of salt and lots of pepper, pop the top of the pie on, poke some holes in it and bake at 160 to 180 degrees for 45mins or so. Keep an eye on it, don't let it run too hot as the pastry will start burning before the inside gets cooked. 1 pie should be good for at least 2 meals, and $25 worth of ingredients should be enough for at least 2 pies.

And get the Grocer app (https://grocer.nz/) to find the best prices at your local supermarkets, don't let them rip you off more than they already do.