I make a berry smoothie at the start of the week and it stays good to have a nice glass full every morning (I am rushing to work - you can decide how much you want daily). Mixed berries (whatever combination of fresh or frozen strawberries, raspberries, blueberries, redcurrants, blackberries, blackcurrant etc that you have to hand). A quarter cup (decent dollop) of porridge oats. Half a cup (slightly larger decent dollop) of Greek yoghurt. Heaped teaspoon of almond butter. About a tablespoon of mixed seeds. Whizz together with apple juice (I tend to whizz it all first and use the apple juice to clean out the smoothie maker into a bottle for the fridge) - use as much apple juice as you want to make it as liquid as you want to drink - or leave it thick and spoonable if preferred. It’s a great way to get good stuff into you in the mornings easily, and the oats help to give you slow burning energy to get through the morning.
I also make a drink of 3 ice cubes of frozen lemon juice, not quite a full teaspoon of grated ginger, 2 heaped teaspoons of honey and a sprinkle of cinnamon, use boiling water to melt the ice and honey, then cool to drinkable with some cold water. I juice a batch of lemons roughly every second weekend and freeze the juice (see mornings rushing - you could just juice one lemon daily) - but it also means it’s easy to prep and easy to make when you might not feel like doing much. I also tend to grate my ginger every Sunday night and use it up over the week.
It’s hard when you’re alone to cook nice things. I do a batch of Mediterranean veggies for roasting, season them up, and use some but bag up most to freeze. Leftovers once cooked also freeze well. Size can vary of the dice, but the size of the veggies in any one batch should be roughly the same so they cook at the same time. Always have onions, garlic (usually whole or half cloves), peppers - then it’s what’s in the fridge and what do I like - mushrooms, cougette, cherry tomatoes (big ones are fine too), sugar snaps/mange tout, french beans, aubergine etc.
chicken joints are lovely roasted and not the hassle of a whole chicken. You could put them on a bed of veggies (see above) or on their own. I love Greek lemon and garlic seasoning (pop in a freezer bag in fridge for an hour or overnight - also freezes well) or put some thyme leaves and a chunk of feta under the skin before cooking. Part boned breasts or bone-in thighs are what I tend to use most. And it doesn’t matter that the packs are made for families as the excess freezes well for another night.
Lamb knuckles roasted low and slow are also lovely and 1 knuckle is plenty for 1 person - but so reminiscing of a full leg of lamb.
I also make batches of good dinners and freeze single portions - I was already freezing in single portions for speed and to easily add another to the pot at home but I am currently solo for work so it makes sense here. Do a spag Bol with loads of veg and a good half bottle of wine for a slow simmer. Or proper curries and stews that need slow cooking for depth of flavour. Most of these work very well frozen and reheated. I find 1 cup is a perfect portion size for me but you could start with 3/4 cup or even 1/2 cup if you don’t want waste - and it’s easy to take a second portion out if you find you are hungry enough. Or serve with lovely crusty bread to mop up extra sauce once your main sauce and carb are finished - buy the part baked rolls in the split packs so you only need to use half at a time, use one for dinner and the second for breakfast next morning, and you have the other half pack for another day. And you can easily turn 1 into garlic or herby or cheesy bread when putting into the oven - garlic and herby butters also freeze well so make it into a log in greaseproof paper and it’s easily sliced even when frozen.
If you want some sweet things, apart from muffins in mugs recipes, a tub of a favourite ice cream and a bag of crumble mix in the freezer are useful to have. Use the crumble over tinned fruit, a single apple peeled and diced, some fresh blackberries you’ve found on brambles outside, a couple of stewed plums or some rhubarb etc. and again, a lot of that fruit can be prepared in larger batches and frozen in single use portions.