JP (Job Point) is used to increase ability Level up and unlock new abilities. It's like an EXP, units mainly gain JP after completing quests.
You can obtain drop items, EXP, and JP by completing quests.
After 4 turns have passed, defeated units turn into white or red crystals. Red crystal gives JP to a unit who takes it.
Units in Barracks (one of the Guild's function) gain JP as time passes. You have to replenish provisions.
To level an ability to 20, you need 5,480 JP in total.
Limited-time story quests JP double-up campaign allows you to farm JP fast.
If a unit in your party (and/or a guest tunit) equips the Job Crystal vision card, the amount of obtained JP is increased.
UR Units & Tier List
Glaciela (Flagbearer of Reform)
How to farm UR Shards Guide