Player Boost and MSQ

[DPZ2]

I wanted to unlock blue mage right away, but I actually want to play paladin and do the MSQ.

You need to complete the 2.0 storyline to get the quest for Blue Mage. There is no 'job skip potion' for Blue Mage. You'll be relying on Paladin for your MSQ even after you get Blue Mage, as the BLU can't directly queue up for dungeon instances via Duty Finder.