also doing DM, and plots, not just your own but participating in other people's too and get completion credits.
Honestly? Not a clue. I haven't had a character go past Level 1, and 2 out of 3 characters are dead. So my advice is try to stay away from PVP. As much as possible. Unless there's such an obvious chance of winning that you jump on the bandwagon.
PvP and plots did it for me, in addition to regular posting. And a lot of the high level characters existed since Day 1 of the timeline