First off, be aware that the build isn’t good. Mage has a slow auto attack speed, can’t crit, and it’s auto attack can only hit one target. These three things that are the foundation of the auto builds of the other classes.
That said, lets optimize.
One circle of pyromancer is required for Enchant Fire. There is a high level dagger that adds 150 fire damage. If you use enchant fire, that damage is added to your auto attacks. And you will be using daggers.
Linker is helpful for farming, but not for flat auto attack damage. The Joint Penalty skill will allow you to hit 5 targets at once with your auto attack. You mostly take this as nothing else at circle 3 is useful.
Thaumaturge is where all the real auto attack damage lies. Swell Right Arm, Swell Left Arm, and Swell Brain combine for a baffling +700 to magic attack, for your entire party. This, if nothing else, will make you useful to your group.
Chrono is currently a trap, I hear. Quicken is currently glitched, and either has no effect or has a massively reduced effect.
My personal plan is wiz-pyro-link-thuam3