Buy a book on veggie growing - there are lots out there. Something which tells you when to do what. Choose the veggies that you and your family like to eat. Don't bother with raised beds unless you decide that is what you want. If you look at Charles Dowding's sites and books (as suggested above) you will see that he has a no dig method which does not need endless strips and squares of wood. Enclosed raised beds seem to have been invented by the sellers of raised beds and end up costing a whole lot of ill-spared cash. Another one who does no timber no dig growing is Bob Flowerdew of the long pigtail.
Potatoes are a good crop to start with as you get a worthwhile product with minimal work and attention while you are getting on with settling in. We put ours in on May 1st here in Scotland but Wales is probably a week or two earlier.
You may have a blank canvas when you arrive, or there may have been a veg patch used before. If there is a patch then you can get in some of your favourite outdoor crops in May. It's too late for garlic, onions and shallots now.
A polytunnel is useful for tender crops such as tomatoes, chillies, peppers, aubergines if you like them, and for bringing on tender outdoor crops when it's still too cold outside (night temps). It is also useful to a smallholder as an emergency place to set up a lambing or mothering-up pen, or to keep your poultry during Bird Flu lockdown. However, I suggest you don't dive right in and buy one straight away. You really need to assess the site for cold spots, prevailing wind, tree shade, aspect, level standing and easy access because once it's up, resiting is a big task. Also, the amount of wind your new place gets will determine whether you need to go for the strongest tunnel on the market or not.
For fruit, choose somewhere for your orchard and get your trees in as soon as you can. Make sure the area does not get waterlogged and that it doesn't catch the east wind. Putting in fruit bushes and canes might be slower as you will need to prepare ground for them. See what others in your area are growing fruitwise. Here we are at 1,000 feet which is the upper limit for apples, and even then we have to grow mostly local varieties, so ask around to see what people have found work well.