Leveling Question

[Niwashi]

Okay so to be clear My job levels at same rate my base class does... my base Class would be my "main" in this case it would be CNJ. correct?

Correct. Once you unlock White Mage, your White Mage level will always be the same as your Conjurer level, because a White Mage is really just a specialized type of Conjurer. This also means WHM has all of your CNJ skills and traits in addition to job-specific WHM ones.

White Mage's secondary class is Arcanist, meaning that's the one that has to be at least level 15 in order to unlock WHM, but using ACN skills as a WHM requires the use of cross-class skill slots, and you don't have access to ACN traits.

Thaumaturge is an optional class. You can unlock WHM without it, but it's useful to level because WHM can also bring in cross-class skills from THM (one of which in particular, Swiftcast, is so highly useful that it's regarded as nearly essential for high-level play).

CNJ, ACN, and THM are each base classes, so they each level separately from the others.