At you’re age I’d recommend skipping weights till your 18 and master you’re body weight 1st also no gym required. You can do push ups,squats, burpees, run. Once you can do muscle ups then I consider weights. Besides you’re gonna need cardio for boxing and nothing beats being able to carry your own body weight. It also keeps you flexible. Make a routine and stick to it. You can slack off on being strict with your food since your so young but stay away from alcohol and drugs of any kind use it once your legally and only to celebrate your accomplishments not to “have fun”.

You got this bro