If you are a skinny guy, and you don't have the "muscle genes" it doesn't mean you can't gain muscle.
Sure, guys that are born with the genes of parents who are bulky are going to have an easier time bulking up.
For them, muscle will come faster and bigger.
However, if you don't have the genes, don't be discouraged.
Every day guys without "the genes" are learning how to train so that they can bulk up, even if they are scrawny.
It doesn't necessarily mean long training sessions for you.
But the sessions might be grueling.
What I mean by grueling is that you have to train hard enough that your body is forced to build new muscle.
Basically you want to get close enough to your capacity in training that your body has no choice but to expand to new levels that it thinks will handle the harder workload.
You will have to train smart.
You're going to have to eat plenty of actual foods to make sure that you have enough calories to gain weight.
Eating shakes and supplements is fine, but it can't be your main focus.
Get plenty of rest.
You will have to train hard, and then get plenty of rest in between your sessions.
This is where many wannabe muscle gainers fail.
They work hard, but they keep working and don't give themselves time to rest.
They don't understand that while you are resting and sleeping is when your growth hormones are working, building new muscle.