first some loots, I did take XP. then, I want to buy item and ability. i choose Gold. my setting level is normal.

On Hard, I am taking the gold early in the game to buy recruit more units. On Normal it is a toss up. On Easy, I took XP.

More often - xp.

On hard, you could intentionally lose battles to gain some gold to put into units. I lost battles early on to build up some gold, which eventually paid off endgame as I had just enough gold to buy the most expensive units and gear.