Step one is to take stock every day or two. What do you have coming up that changes any of your time requirements? What do you have in the fridge that needs to be used up?
Step two is to shop more frequently, or at least have an extra day or two where you could stop by the grocery store if you need to. It can be easier to figure out two days at a time than it is seven or more. At the store bulk bins are your friend. You can buy as small of a quantity as you need. Be aware of the policies of the stores you shop at. Publix sells produce by the pound, but often most of what is on the shelf is packed up and ready for a family of four. If you look around, you'll likely find a tiny section of loose items that you can choose from. If you ask, they will also split the package for you. My personal rule with shopping is that if I cannot think of three uses for it then it does not go in my basket. If I still want it later I can always search out some recipes and pick it up on the next trip. And always use a basket instead of a cart. I also try and limit my new or weird items to one or two. This way you don't have to try to figure out what to do with hoisin, fingerling potatoes, eggplant, tahini, orange sauce and skyr, all before they go bad.
Which brings us to recipes. You'll likely work up a certain amount of staples from a base set of ingredients. For those one or two new or weird items, use up one before you work on the next one. So you might work your way through a bottle of hoisin and then work your way through a bottle of BBQ sauce. Have a few staples in all the time (ketchup and mayo for example), but plan on just one extra rotation slot and use up one before you open something new.
Since you have little to no fridge and freezer space, look to shelf stable options for perishables like produce. Canned foods give you more play than fresh. Dried is another option. What you do buy fresh, buy hardier options. Which means that berries can easily spoil in a few days. Apples can keep for two weeks or so. Carrots, cabbage potatoes and onions are hardy, avocados are finicky. If you don't have time to use them in the next day or two, stick to the hardier fresh options.
I also find that cooking ingredients rather than meals helps. Which means I can cook up some cabbage, onions and mushrooms on day one. A portion I will take out for next day's lo mein and the rest I will add five spice to and braise. I cook up a pot of rice today to have under the brasied cabbage. Day two I use up my veg blend with some pasta, ginger and soy sauce to make lo mein. Day three I can use the rice to make fried rice or top it with broccoli and cheese. Day four I might have broccoli and cheese over baked potatoes. Day five I could use up the last of the potatoes and cabbage in colcannon. By cooking ingredients and mixing them together I avoid the trap of cooking for four and getting so sick of the same thing for lunch and dinner all the time until it's finally over. Plan on cooking one new thing and using up something that you have already made. It's the same idea as roasting a chicken on Sunday and making soup with the bones. You have some pieces of chicken on Sunday and use leftovers Monday and Tuesday in different things (sandwiches, fajitas, casserole, salads) for lunch and dinner. Then you have the soup on Wednesday. It's just when you are by yourself you have to scale back. You need one zucchini, not four. You need a 1 lb bird, not a 5 lb one.
-google first. ask questions later.