As someone who cooks for themselves alone a lot, how can I improve my efficiency/speed of prep, cooking, clean up etc.
Cook in large batches. The difference in time between preparing a single serving and, say, six servings is far, far less than 6x.
Pick the kind of meals that are okay to be refrigerated/frozen, or otherwise preserved, obtain a bunch of single meal sized tupperware boxes, make sure to have room in your refrigerator/freezer/pantry, and prepare quite a few meals of the same dish at a time. Eat one serving, leave the rest "for later".
Don't go about it the way you cook the next batch only when current one runs out, but stagger that - a week of cooking six servings of a new dish every day, leaves you with five more weeks worth of varied meals. Label your food, with type and date so that you don't leave anything too long and you know what you have (it's quite hard to tell some foods apart when they are frozen).
You also don't need to make complete meals - you can prepare some more time-consuming ingredients in large batches, then make the readily made parts of the meal as needed, fresh - e.g. prepare several spaghetti sauces with meat, leaving cooking pasta and adding fresh seasoning as you prepare individual meals.
The make multiple servings or prep ingredients for multiple dishes is valid, but at a price. Some items take it better than others, but even with an item like carrots that hold up well to prep days in advance, there is still a loss of quality compared to prep just prior to use, the degrading is simply slower than for some other items. On things like that you almost have to pick and choose and decide which is more important to you, the prep time or the improved freshness.
Even when not preparing for one, I am very guilty of the too many bowl syndrome, as I am accused of dirtying every item in the kitchen to make one bowl of cold cereal. Something I find that works for some things though is divided plates which I grew up using for picnics or camping. If I make something like stir-fry, I can prep my items and group them in the order I want to add them rather than having half a dozen containers of ingredients, I end up with one but still get them separated by cooking time and order.