Add Subclass:
You aren't eligible to add a subclass at this time.
To add a subclass, you must meet the following conditions:
First, you must obtain Mimir's Elixir. To find out more about this quest, speak with Magister Ladd at the Ivory Tower of Oren.
You must also have completed the "Fate's Whisper" quest from Maestro Reorin, who can be found in a hut east of the Town of Oren.
Secondly, your current occupation must be the second or third job, and all of your subclasses must be at Level 75 or above. For example, if your current subclasses are Temple Knight and Silver Ranger, both Temple Knight and Silver Ranger must have reached 75 if you are to add a third subclass.
Thirdly, all characters are limited to three subclasses. If any character already has three subclasses, he or she cannot add a new one.