Here's an interesting blog on the subject:
Cooking for OneMost times, cooking for one (or one and one-half, as I do at least every third day) isn't very difficult: it's
shopping for one that's a challenge. It's easy to
make a single portion of protein, veg, and starch - but they don't make it easy for you to
buy just one portion. It's not impossible, however - for instance, you could ask at the counter to get a package of meat split into a single-serve portion, or you can always repackage and freeze when you get home. Produce is usually more expensive the smaller you get it (one potato can cost as much as a 3 lb bag,) so you have to decide where the point of diminishing returns is: how much will you throw away as opposed to the higher cost of buying just one. Pastas, rice, and beans keep forever - though you'll have to have a strategy for using up a can (you can always make bean dip for snacks with the leftovers) Dairy actually keeps a while, and egg dishes are terrific for quick meals for one.
You might want to invest in a good toaster-oven (it seems silly to heat up your entire oven to roast a leg/thigh pinwheel, but you can do it in a toaster oven quite easily.) Other than that, if you think about it, most simple meals don't involve portions at all: you make the recipe and add on or reduce servings as you go, think steak, fish, chicken, pork chop, hamburger, sausage. Then you just add a side: a broccoli spear, a handful of green beans or peas, baked beans, buttered noodles or rice, a baked potato.