My favourite cheap recipe is lentil salad. It is really easy to cook:
Cook 2 garlic cloves (crushed), a bit of ginger (grated or powdered) and cumin seeds for 2 minutes
Add 300g split peas / split red lentils (I've done it with both, both yummy)
Add 700ml water with one soup cube in (I use a veggie one)
Cook for 20 minutes until the lentils are cooked and all the water is gone
Stir in some baby spinach and top with caramelised red onions (just onions and a bit of balsamic vinegar in a pan until they taste sweet) + goat's cheese if I can afford it.
Voila! Dinner for less than 400 calories and €1 per person