Hi I understand your concern. For weight gain have heavy dinner comprised of wholesome cereals and protein meals comprised of foods like dal, rajma, lobia, ragi, barley, jowar, if non veg then eggs, fish or lean meat. Have dates, anjeer, banana milk shakes.
Next Steps
You should do a check up for your general hormonal balance n also absorption levels are ok or not. If these parameters are ok, you will get results after following these. Try to exercise n do cardio exercise daily.
Health Tips
I am from Delhi too if you want to consult for a customized diet plan suited for your body type, you are most welcome.