Get a Dragon full helmet. You may get this by killing mithril dragons (Level 302) or by burning chewed bones in a pyre ship. These are also obtained by mithril dragons as well. Note that it is very rare to get a dragon full helmet.
Find the Dragon platebody. This can be obtained by killing tormented demons and getting all three of the platebody parts. Then you must get access to the dragon forge. He will then smith it to a platebody. Note again this is very rare and the fire dragon will do damage unless you are wearing ice gloves.
Buy the dragon gauntlets. These can be obtained by playing Fist of Guthix and saving 150 points. Note that the Fist of Guthix is slowly becoming empty so you may want to just buy it instead of waiting for 15+ people to come.
Steal some dragon platelegs. These can be obtained by killing several animals including metal dragons. This is not as rare as the others.