I'm starting a game of Radiant Historia, and as with most RPGs I'm under the pressure of making a choice as to whether I should spend freely or save it all up for a rainy day. Do I have to be wise in spending in this game or do I spend on weapons, armor, etc freely?
You can always fight random battles to make more money, so essentially no, money isn't an issue.
If you fight all the enemies you come across during the normal course of the game (without running past them, or away from them), you'll have enough money already that you won't have to farm.
You can still farm though, and it's not difficult.