Personally this is a bit of uncharted territory at the moment of writing this guide, once you have reached class 4, you will need to go out into more hazardous maps, like Deep Dungeon or Swamp of Calmness.

Those two maps should be your early bread and butter for XP. Kubera mines and Abyss Atlans are great once you reach the required levels. After that its up to you! The way up to level 1200 is slow, but rewarding! Those points for the enhanced skill tree are totally worth it!