To get 3000 calories in low cost you have to eat a lot and along with that you have to much on a lot of lentils. And if milk is available in your budget then milk,paneer should be on your menu as well. If you are not allergic to eggs then, at least 2-3 eggs per day will provide good protein and calories. And of course if you can afford at least 50 grams a chicken per day that would be awesome. Apart from this you should get your main calories from rice. And that is how you can eat 3k calories of food in India.