trying to gain weight on a budget!!

more calories = more food = more money!
I know rice, potatoes, pasta, and beans are all cheap, but they are all very carb heavy!
Nuts and nut butters are great but nuts are expensive! any other ideas for cheap healthy food that isn't too carb heavy (I'm not doing low carb - obv i need carbs for weight gain, just trying to not go overboard). I am a vegetarian. I do not eat much dairy other than yogurt. I have just added eggs into my diet as well, however I am again trying to not go overboard with them (maybe 7/week max?)