I intend to gain weight and I want a muscular physique, and I'm going to work out. Will whey protein help me in weight and muscle gain? And which one should I take, Isolate or Concentrate? My weight is 63 kilograms (approx 138 pounds) and height is 5'9.5"
Protein is calories; additional calories will help gain weight.
It's important to get fast-acting proteins (whey) and high-glycemic-index carbs very soon after working out (15-30 minutes). Isolate is "better", but more expensive. Is it enough better that cost shouldn't be a factor? Probably not.
I personally tends towards a mix--some fast-acting, very pure (isolates), BCAAs for specifics, concentrates, and slower-acting, to cover my post-workout bases and to make sure there's a steady stream of protein.
Casein-only (or primarily, at least) is good for night-time since it's slow-acting. Can be a powder, or just cottage cheese (sort of our version of uncompressed paneer) because it's tasty, and I like to eat.