I actually believe the best to gain exp and become emersed in the story line/game should be via quest completion, not simply grinding, thus as your going through the motion of completing a quest your also gain exp from you actions. However the quests themself/ leves are quite boring at times.

Also I have found in this game players do not seem to communicate much at all unlike say lineage 2. Which doesn't really help much when looking to form parties to gain exp.