He's 16... He could gain 50 pounds from 16-18 if he wanted. Obviously there's tons of factors.. But it's still possible.
Best advice to OP is eat 1.5 g of protein per day, 80g fat per day, and the rest of your calories from low glycemic/low sugar carbs. Center your carbs around breakfast, pre and post workout.
Lift simple and heavy. 5x5 is great for squats deads rows overhead press and bench. Do lots of pull-ups too. Focus on those things and getting your food in. Less time in the gym is better for you. Do enough to cause muscle damage (for growth) but don't over train your body to the point it can't recover and grow.
I would implement some prowler pulls and pushes and variations of it too. That thing is great.
Even if you don't gain 10 or 15 pounds... There's no sense in NOT trying.