Yes and no.
Quite simply, you don't level Jobs, you level classes.
Jobs are specializations of your Class. So, if you want to be a Monk, you need to level Pugilist. When you unlock Monk It requires pug to 30, and I forget which class to 15), you get abilities from your main (pug), and only 2 sub classes (they are specific, and I don't remember them off hand).
An example of this would be Paladin which I do know off hand, it is Gla and Whm, with Mrd as the one that it will also inherit abilities from.
As you progress in Gladiator levels, you get high enough to now unlock new Paladin abilities by completing quests. So, you level your class, and once your class is high enough, you quest for new abilities for your job.
So, the biggest benefit is the fact that you get access to abilities you normally wouldn't get from any other class.
The biggest penalty is that you lose abilities from all other classes (e.g. currently only Paladin, White mage, and Bard can raise as Jobs).
It allows for an interesting focused Class system, but still allowing for the use of the unfocused class system that was originally created (you can pick and choose different abilities that are multi-classable).
If it has been quite a while since you have played, they did change it so now, only some of the abilities from each class can be used cross class. And if you are playing a class, you can choose any one (typically people who are in a class based party do it strictly for the additional need for raise) for a maximum of 10 additional abilities. If you are playing a Job, you can only add 5 additional cross class abilities from 2 designated classes. At level 50 this will result in the same bonus of 10 additional abilities to your Class/Job (for classes it's a flat 10, for jobs it's 5 cross class, and 5 job abilities).
But, where you gain your class abilities for free, you do have to quest your job abilities (and you get your AF in the process).
So, with you being a level 35 pug, you need to level either archer or lancer (I think it's lancer) to 15. Once you get 15 you will not need to level it again unless you want to, and then you can unlock Mnk. From that point on, you can level as Monk, and the exp will go onto your pug. Your pug will level up, and you will unlock new Mnk abilities as you get your pug up, and quest them.
I hope that makes sense:).