Pls Suggest Low cost food items for weight gain. (26M, 35 Kg severely underweight)

Hi guys, I just checked my BMI score which is 13.7 and it shows that it's under severely underweight category in Red colour. I'm a 26M, 5 ft" 3 in , & I weigh just 35 kgs. I'm currently unemployed, so I can't afford expensive food items/products for weight gain. So pls suggest me some low cost food items and weight gain powders etc. I did a quick search & these are a few that show up most. Eggs, Milk, Curd, Peanut butter, Oats, Dates, Bananas & potatoes Are these the best choice for weight gain on low budget ?? Or are there any better alternatives? ls there anything I can add to/remove from list? I'm also thinking about trying any weight gain powder but I found some people saying that it contains too much sugar & some stuff which is bad and so it's not worth buying. what do u guys think? If there is any good low cost weight gain powders pls tell me it's name or send me it's link. & How much weight can I gain in just a month realistically ???