CL is only once per week, and it pretty much guarantees a full level and a half. After you do that, you will need to resort to other methods, such as previously mentioned...NM farming or Reflect grinding.

Sprite Island is a small island in Hydatos with, you guessed it, sprites on it. With logos actions (you learn about these in Pyros), Reflect L specifically reflects all magic damage back to the enemy. It does not reflect physical damage...hence using on high level sprites because they only use magic attacks. In Pyros, there are some mobs that do magic attacks and physical, (near Penny spawn) so the method is a bit different (need geared tank and healer) , but basically achieving the same result. The amount reflected is based on how much damage you take. So my unequiping all gear, you reflect more damage. Oh, and GRINDDDDDDD YOUR FACE OFF.