Good addition to pokemon team?

Definately keep Dragonite, I am not a huge fan of Gyarados, and I really like Magnezone. I think Your Magnezone has a good move set, so I would switch Gyarados. I would recomend replacing it with a ground type, being strong against fire (which is strong on Magnezone) and electric (Which is good against Dragonite). A good ground type would be Donphan, Flygon, and Rhyperior. I personally like Donphan the best plus he is easy to get so I would choose Donphan.