@ally1 - do you have a freezer, and do you have a slow cooker?
I must admit my OH does virtually all our main meal cooking. I do breakfasts and lunches. But, when I'm on my own, I obviously have to do it all. I'll be having a few weeks of solo living from next week, when I come back to UK. He comes back in a few weeks.
In the time I have solo cooked, as a diabetic (a month back in UK in February), I found cooking, then freezing the excess portions ideal. I also got into the habit of ensuring, if I was putting anything into the freezer I portioned it up, or at least ensured things were separated, so that I could easily access a single portion of something to minimise waste. I also used the slow cooker to get casseroles, or soups on the go, with minimal fuss or intervention.
I was astonished how little I was spending on food shopping, without alcohol or some of the treats we might have had, so that was a bonus.
I agree it makes sense to try hard for a period of cooking from scratch. It doesn't all have to be expensive. Roast belly pork, with crackling is inexpensive, and low carb. A batch of chilli, using a quality mince can be mega tasty. Lemon pepper on chicken breast or frozen fish is delicious, and again can be at a modest cost.
I also tend to make a Tupperware box of undressed salad - rocket, grated carrot, red onion or shallot, a pepper, shredded cabbage and whatever else is around. Give it a shake and take a portion out at mealtimes, and it lasts 2 of us a couple of days. We tend to dress the salad as we go, so that we chan choose a dressing to match whatever else we are eating. One of my favourite lunches is a handful of salad, open a tinny of sardines in lemon oil or hot Louisiana sauce, and toss through the salad, and enjoy.