If you are not intending to skip the story, then do not bother with the level boost either. There is more than enough XP from the quests around to consistently out level the MSQ requirements.
The out levelling from the 2.0 - 2.55 story parts will usually have you at lv55ish before you start the 3.0 story.
The out levelling from the 3.0 - 3.55 story parts will usually have you at lv67ish before you start the 4.0 story.

Basically, level boost is only really helpful to bring a second job upto 60, thus, avoiding the levelling grind after you have completed all the quests already.