mass gain

A clean bulk is one thing, but gains so slow you can't measure them might not be useful.
The old Russian training principles weren't conceived with your goals in mind.
Smart programming, exercise selection, and execution can go a long way to reducing the risk of injury.
Ditch the self-limiting thoughts that have been holding you back and flip your thinking to a growth mindset.
Packing on the muscle doesn't have to be complicated; you just have to be committed.
My calorie calculator will tell you the proper number of calories to consume, based on your daily activity level.