Start with what you like to eat.
I grow a few pea plats as fresh peas eaten straight out the pod are lovely, not shelling vast rows of peas to put in the freezer is a little pointless...
I love broad beans, you can put them in now to overwinter ready for the spring, and like them enough to happily spend ghalf an hour shelling them.
Freshly dug new potatoes are lovely, and it's great digging them up, my 45 y o DH was quite excited by that, who'd have thought?
Spinach and chard are easy, as are mixed salad leaves and courgettes, all sorts of different colours. Beetroot and carrots are easy too, and some radish as they are so quick. Garlic also very easy and you can plant that now too.
Once you get into broccoli, I love purple sprouting, you have to probably net them to get a decent crop.
I grow a lot of fruit, black currant, raspberries and strawberries, as they are really low maintenance. Plant them all in the same space as you might want to put a fruit cage up if you really get into it and have stealing birds...
There's a grow you own website and an allotment one that is really good.