A few tips since you asked:
1) Make sure you keep up with your campaign quests as you level. They are usually huge exp boosts and sometimes give decent armor or weapons for their level.
2) Level your essencetapping while you level, especially on the fast-track server. You can level your aethertapping as well, but that's a bit harder to do until you get more flight-time later in the game on armor and wings.
3) Coin repeatables are your friend if you don't mind it being incredibly grindy. I believe they start at level 20 and you can get full sets of armor + weapons by using those coins and they usually give nice exp rewards.
4) When selling stuff on the trade broker, be sure to actually check the going rate for that item in the buy tab instead of going off the default price the broker window starts with when trying to sell. 9 times out of 10, the going rate is higher than the default price. A lot of people don't realize this and price things incredibly lower than they should.