My goal is to gain 25 lbs. What are best weight training exercises?
Basic foundational compound exercises
Squats, deadlifts, Bench, overhead press, pullups (or lat Pulldown), rows (many varieties but seated Cable rows is good)
Workouts i pulled from aworkoutroutine.com where the author gives straightforward info on why these are ideal for beginners. These exercises are the foundation of any more advanced isolation program as well.
Eat a lot of protein, eat healthy, drink a lot of water and rest between heavy workouts. You could do a creatine supplement. I can gain quick with creatine though some is water weight.