The best way to obtain JP without any element is by using the "JP UP" skill from the Freelancer tree, at level 9. This skill will allow you to multiply the JP you win in any battle by x1.2 and it has a cost of 1 space.
And although it does seem little, it will be very useful, especially if you combine it with accessories and factors that you will find as you progress.
That's all you have to know about how to get JP in Bravely Default 2, we hope it was very useful and you get as much JP as possible.