Hi there I understand your concern. Your weight should be 77 kgs. Mass gainer is not a good idea you can increase your weight by following proper diet. Include calorie dense food like dates,nuts,avocado,cream,butter,peanut butter in your diet. martial arts will not helps to increase weight but definitely you will see good change in stamina.  Eat small frequent meals. Drink plenty of water. Avoid walks after you have you meal.