first your nutrition has to be good, otherwise the protein shakes are useless. I sometimes drink them after a workout for better recovery (protein and carbs + creatine) imo theyre more for bodybuilders, im training more for strenght so I dont care much about those mass gainers a lot of people think that theyre like some magic potions or just drink them because others do, so they arent needed but they can help if used as they should be