Just fight every enemy you see for the first 10 chapters, and there's no real need to do any more than that until chapter 11, where you'll want to do at least some grinding for CP. There is one hallway in chapter 9 with some soldiers that can respawn, are easily dispatched, and have a good chance of dropping some items that can be sold for a decent amount of gil for that time, but I wouldn't recommend bothering stopping to grind anywhere before that.

You won't really need to farm for gil until postgame.