I think he just missed out a comma between speedball and weights lol.
You shouldnt start actual boxing training (heavybag) by yourself, you need to get properly taught how to throw the punches correctly (you might develop bad habits which wont be helpful when you start properly).
Try to get to the boxing gym if you can, but if not work on running, skipping, weights (they do any damage, just dont lift too heavy if your 13) and any other cardio (bike, swimming etc), speedball's probably ok to use as well because it more about arm endurance than technique.