The very best food you can eat is wild food. It generally has better nutrition than cultivated food, it is local and you can pick it fresh just before you want to eat it. I’ve been eating a salad with wild greens almost every day for over 10 years now. This has been while living in the UK, Portugal and Spain so I know a range of plants from different areas. I will show you the plants I know which are in season here, plus we can look in books at some common edible plants which are out of season and/or grow only in the UK.
I can show you salad leaves, plus some wild fruit and flowers but at the moment I don’t know much about mushrooms.