Every time I've traveled in Europe, it has been really hard for me to find vegetarian food. England seems to have it figured out, but Germany and Austria were the worst for me!
For a vegetable garden, it depends on what you are looking for. The most calorie dense crop you can grow is potatoes. That means that an acre of potatoes would feed more people than an acre of any other food. But potatoes are boring! The least calorie dense crop is squash, but I grow far more squash than potatoes. You can grow varieties of squash that are simply not available in the grocery because they don't store well.
Ok, so my recommendations for a first time gardener are almost always squash, tomatoes and peppers. They are all easy to grow (if you have the right weather - I think Slovenia would be warm enough) and they are so much better than store varieties. Plus, one or two plants of each of those will likely provide all the squash, tomatoes and peppers you can possibly eat by yourself!
I am trying to grow all of the vegetables for my family. I am currently growing turnips, corn, okra, peanuts, tomatillos, peppers, tomatoes, eggplant, summer squash, winter squash, black eyed peas, green beans, watermelon, sweet potatoes, muskmelons and spinach (I think I got them all!). Our potato crop failed this year and that was a real drag. We've also had to buy onions and most of the lettuce we've been eating. But we probably grow about 50% of the vegetables for the family now. It's fun!