Where can you get serious mass gainer (body building supplement)?

Body building. You don't need a bodybuilding supplement - what you need is a combination of a good diet and regular exercise. For the diet I recommend you go on-line to "NuVal" and learn the good, not so good, and bad for you foods. If you want to body build a visit or two to a trainer would not hurt if you can afford it. Otherwise use common sense and don't overdo (or underdo) the activities.