There is one big question:
Auto potion or dont auto potion.
Giving everyone auto potion (its a chemist skill) lets you sort of easy mode the game a bit, you will just heal by the amount of your smallest potion size and just tank hits but I think makes the game less interesting.
One thing you should get right away for everyone is Gain Jp up. I wouldn’t use it in a big battle unless you dont have a better skill for the slot but for moving from town to town the skill is invaluable.
Id also gain moves units can do nearly every turn like yell or throw stone so that you can get some kind of JP even if you are just moving a unit. It really adds up. And like gain JP up it might take up a slot you want to use for something more practical or cool in harder battles.
I first played the game by looking through the job skills and being like “OOH that combo would be cool to have!” then making a plan to get there and write it down so you can keep on track. This mostly seem to yield fun results. Making sure you have a fun new skill to try out makes grinding for levels fun. You can also take into consideration class stat growth. I find the stat growths mostly intuitive, archers get more precise, mages get more faith, knights get stronger. Just think about how you want the unit to be and aim in that general direction.
I like to make up little stories for every unit in terms of what their ambitions and background are. Then as they grow its just make for some good brain candy.
A few of the hot options:
~ Guns let you project damage finitely in a straight line.
~ The Dragoon/Lancer Jump skill not only lets you do heavy physical damage prettty far from your standing position it also takes a character out of play, ie they cant be hit till they land turns later. This means those characters can run straight into what would be ambushes.
~ Stealing lets you not only gain potentially unique and powerful equipment it lets you disarm some incredibly strong opponents. Especially if the % is low the feeling of landing it rules.