Goliath

Will come naturally through play. If you cant wait or need it for a community event asap travel to Murkwood (first World) and then go south from your camp to find a large group of Dodos. Aggro them and let them bunch up then launch your special attacks or just kill them normally. They can be respawned by traveling elsewhere or after some time spent in the game. Around the same map you should also find a few more groups if need be. It will go a long way towards getting you the kills but I wouldnt fully grind it out on that map alone.