For gaining weight, try to eat more proteins like pulses, milk, milk products, cheese, paneer etc.. And more fats like oil, ghee, butter etc.. Examples of food items - sprouts, sweets, dals, Khichadi with more pulses and oil etc.. Eat more vegetables and fruits to meet requirement of vitamins and minerals. There is no magic product which can increase weight, so don t be deceived by these products which claim magical solutions. And most importantly try to accept and love yourself as you are, which is more important than anything else. Don t compare yourself with your friends in these aspects. Instead try to be better human being than your friends, which matters.