Accept General Hun'Gar's "Do You Even Brawl" quest from /deathpitarena. Then defeat enemies from the opposing team at /deathpitbrawl. This quest can only be done once. After that, farm the below quests.
"Flex For Hun'Gar" and "Pummel For Hun'Gar": Defeat enemy Restorers and Brawlers. If you're on the Blue team, keep walking right to find them.
"Destroy For Hun'Gar": If you can, also defeat the enemy's General. You will need a good soloing class for this.