Every alternate class/job you play on your character gets the same number of attribute points to spend as the original class you started with.

So, for example, if you begin as conjurer and become a white mage and level that up to 50, you will have a total of 30 points to spend on things like mind, piety, etc.

Then if you decide you want to also play bard, you begin as a level 1 archer and can eventually level that up, become a bard and get to level 50. You will receive a new set of 30 attribute points to spend on your archer/bard class for dexterity.

As for leveling these alt class/jobs, I have always done a combination of Fates and dugenons as well as all of the class/job quests that you can get.