Confused about Classes and Jobs

[Niwashi]

So, if I were to level Pugilist and Lancer to level 30, and then level Marauder to level 15, would I be some sort of Monk/Dragoon hybrid and be able to use abilities from both of those jobs with my main class (Pugilist)?

Well, you'd sort of be a Monk/Dragoon hybrid in the sense that your character would be someone who had learned both how to be a monk and how to be a dragoon. You'd be able to unlock both of them and alternate between them any time you like. But at any given moment you're one or the other. They don't merge into a superclass that combines both. You can unlock and level as many of the game's classes and jobs as you'd like, but can only play one of them at a time, with just certain select skills available to use cross-class from other classes you've also leveled.