Hi
As i said before, until you're 40, there will be XP gap, even on P2P server. You need to do all the quests ! If you like PVP, kill some players too.
Eljune and Coba are painfull, there isn't so much quests (with great XP rewards) so kill every mobs you encounter, kill thoses 100 mobs from historian's quests, do reputations quests, everything.
You can also farm dungeon with mercs, Tensess 2 for exemple, or Tensess 1 if you don't have access to Tensess 2 now.
You just need to wait 30min to 1hour between each try to let the dungeon reset.
I think that you already had thoses advices from all other players.
Once you'll be 40, it will be much easier, and you will be able to choose your quests. Until then, no choice.