What protien shake to buy?Watch
I know and I agree that they have to consume more carbs and kcalories however this does not have to come from a mass gainer which has 47g of carbs. It would be a lot better for him to create his own mass gainer at home with 2 scoops of whey isolate, 100g of oats, a milk replacement, 1 tbsp of peanut butter and any other ingredient he likes, this would be a lot more cheaper, your 'pro gainer' is freaking 45 dollars for 16 servings, would have more kcalories, I make this everyday and those ingredients alone amount to around 1000kcalories, and it would have a lot more micronutrients and a bunch of unsaturated fats from the peanut butter.
Furthermore you're mass gainer has lactose containing products which would not agree with OP's stomach as he is lactose intolerant and is amino spiked with glutamine so it doesn't actually contain 60g of 'protein'.
There is absolutely no reason for him to go with you're ON pro gainer.