I think there is a lot of negative on here regarding the food situation.
It is easy to make flat bread over a camp fire and bread provides a lot of calories and goes with everything. Vary the type of four and you have variety. Add some butter/mag/oil to that and you have plenty of calories.
Soup and stews or casseroles are easy to make and with a touch of baking powder dumplings can be added to create variety.
Cooking eggs in the soup/stew adds variety. We are not talking about 3 meals a day made for €1 of there is more than 1 person.
Beans and pulses will add necessary protein, again not that expensive. Red lentils are great in this aspect, but baken beans are also great.
Consider splashing out on some tahini or halva as well. Both are made from sesame seed paste and very rich in nutrients and calories. Tahini can be added to most dishes and in particular mixed with something like grape molasses, date molasses (my favourite) or just and sweet sugary substance and spread on bread for breakfast. Halva is a great energy boost during the day and a good nutrient hit if running low and far better for you nutritionally than straight sugar like jelly babies. We lived off it through eastern Europe on our big tour, but it is widely available nowadays if you know where to look for it.
Nettles have already been mentioned and they are very nutritious, something people often don't realise and dismiss. And there are plenty of edible tree leaves if you know what you are doing. They may not add many calories but they do add variety, the same with flowers and petals, many of which are edible.
Oatmeal is a good choice for breakfast and any berries picked (query on time of year, I forget now) just checked and it is June, so start of the very season, berries will add the necessary vit c to the daily diet but from experience they do take a while to pick (for 2 people picking for 2 put half an hour side and remember to have a suitable container handy), but it is easily doable (I have done it and so have both my oh and I together until the season finished on us in mid September).
Eating off the land is not that hard with the right training and practice. It's the latter that is more important! Time and patience are key.
Of you want anymore nutritional advice, please come over to the CookingBites forum, the link is at the top of the page. It is another of the site owner's forums.
Edit: I would have loved to have come but sadly I doubt my back injury will have recovered enough by June for me to join you.