Please tell me what to eat for breakfast and what to eat to gain little body weight.

I think that the better way to start your day is with an healthy breakfast: some yogurt with granola, an orange juice and tea or coffee will do the trick

Focus on protein, fiber, healthy fats and complex carbs. Choose healthy whole foods and eat a bigger portion. Make sure you eat lots of protein and fiber. Establish what are your caloric needs and try to eat in a little surplus. Try eggs, cottage cheese, avocado, full fat dairy, oatmeal.