Got an allotment this year. Start growing a variety of things, see what works and what doesn't. Here are some things I have been growing.

Jerusalem artichokes seem to be growing nicely, not dug them up yet though to see how big they are underground.

Tried garlic and it struggled, bulbs are all tiny. Ground likely too damp for them or planted too deep. Might try walking onions next year

Radishes, the greens were nice, roots have mostly been nibbled by maggots though.

Good king Henry/some variety of goosefoot, planted seeds and feels like I shouldn't have bothered as it's growing everywhere wether I want it to or not. Perennial plant and you can eat the leaves like spinach, seeds like quinoa, shoots like asparagus.

Perennial kale - just getting eaten by insects so probably going to give up on that soon.

Rhubarb and blackcurrants, recently planted so not had much time to comment on them yet. Seen other people nearby with fair size rhubarbs though so hopefully it will go well. Might make it into wine.

I would suggest getting at least a few things that don't require buying constantly new seeds. That is my longer term plan with things like the blackcurrants, take cuttings of the bush to propagate it further - it came with a label saying propagation is prohibited which I take as a challenge. Plant piracy!

Quick edit - also in my garden at home I am growing rosemary, sage and bay which are all doing well. Got mint in pots which is struggling a bit, partly from neglect. Should be ok if I water it a bit more. A large barrel for it to grow in could be nice tbh. Stick holes near the bottom on the side so the bottom holds a reservoir of water is also a tempting idea, as long as it's a deep enough barrel that the standing water is reasonably below the surface.