Thanks for the query.
Firstly understand that weight gain is very dependent on genetics and metabolism.
It is important to know that just
eating just two heavy meals a day will not help. Eating the right foods at the right time is very important.
Eat meals at frequent intervals.
Eat a mid meal between each main meal.
Avoid junk foods.
Include dairy, eggs, nuts, fruits in your meals.
Avoid alcohol and smoking.
Exercise at least thrice a week.
Even if you were to take medicines or supplements they will not work in isolation You need to have a calorie and nutrient dense meal. So, first try to improve your diet
before you decide to start any supplement.