A different slant on some topics .... so I'd say the following!

Frozen vegetables have more vitamins and are generally better for you than fresh vegetables which of course are not fresh .... and make much more sense for a single cook. No waste. Portion control.

Frozen fish is much much better than fresh unless you can buy it off of a fishing boat. You can also split packs of two fish into one. I feel dumb at my life long presumption that fresh is better than frozen. It isn't - the only way you can tell is that frozen tastes fresher. Sea bass is a favourite and frozen haddock in batter for fish and chips. Frozen chips are really good these days. We only ise them and never fry.

I think the most important thing you can have is some freezer space and a supply of small square plastic reusable containers. I'd see this as a game changer. Being able to make a batch of fresh bolognese sauce and split them into single portions means you are always eating superior home cooked food and done in moments. Same for stuff like curries which always improve when reheated. Cooking for one is a great excuse to have a lovely reassuring stock of great home cooked stuff in the freezer in small packs. It is always going to be better than bought and normally much cheaper.