To all the muscle-gifted folks~ What do you think of this protein supplement?

It's my 3rd day of working out.
The trainer stationed at my company recommended a mass gainer supplement, saying it has the best cost-performance ratio.
But aren't the sodium and sugar levels a bit high? I thought that when building muscle, you're supposed to avoid almost all carbohydrates and salt..
When I asked if people building muscle mainly eat egg whites, chicken breast, and salads without sauce, he said that's what people do when preparing for a competition, and for now, I should just eat normally without being picky.
Since I'm about 188-189cm and 75kg (skinny), it seems like he wants me to gain weight first and then lose the fat.
It's not that I don't trust the trainer, I just wanted to hear other people's opinions haha.
Is a mass gainer okay?