KBAP is much harder, especially in the beginning, as Ilmarin said. Also, mages are now the hardest class, not the easiest. Basically, in the first part you were nuking with your spells, but now the mage role is more of a summoner - once I realized that, things started going more smoothly. I haven't finished the game yet, but I do feel it's getting easier after around Verona. Also note that you'll get leadership as a mage, so eventually all the fights will be "Lethal" to you, even if you've already killed everything you can. My warrior playthrough feels much easier (haven't yet reached Verona, but it's definitely easier so far).
Anyway, on strategy: gold for troops shouldn't ever be a problem, simply because you aren't supposed to lose any troops in battle. That's basically the core game principle here, and now there's even an explicit reward for pulling it off (more leadership via the medal). Of course, to do that, you'll probably want to have some means of ressurecting troops - Paladins or Inquisitors, and a means of getting fodder (Royal Griffons, Royal Thorns...). After that, it's just a matter of picking your battles carefully; also, be sure to "kite" (draw out the enemy troop and then run around it to get the goodies) whatever treasure you can, particulary leadership flags.
A lot of the game is random: enemy troop composition, troops and artifacts available in shops, shrines and some treasure. Of course, this is great for replayability, but you can also get pretty screwed if you don't get good units/equipment for your chosen class. Finally, if I had to pick one thing to change, I'd like it very much if I could recruit my chosen troops without going back to the shop, after the first time. After a while, it becomes very annoying to run back to previous islands to "fill up". In fact, that's what always turns me away from the game after a while - I haven't actually finished a single playthrough, in both KB games, precisely because this gets too tedious after a while.