My current progress in this game is that my party has reached levels 13-15. Lowest kills = ninja (148), highest = fighter (443). Gold pieces are 8.5K. I've explored the obvious initial areas, including the early initial "road areas", Trynton, and also the southern part of the Swamp.

I see that Crock has some nice spellbooks for sale, but they are expensive. Is there a way that I can boost my cash flow, so that I can afford some of them? I also need to get the AoH too. I read of a trick to make heavy healing potions from other lesser strength healing potions and then sell them, but really, I feel as if I may as well simply use a save game editor, and add gold to my party that way.

One thing I'm not doing is sticking much to the storyline, and so I don't know if I'm missing out on receiving large amounts of gold by completing certain quest/tasks. When I find an NPC, I don't tend to talk to them much, as I don't really find that side of the game all that interesting yet. I'm more interested in the fighting atm.

Given that, am I looking for a place where I can continue fighting, but expect to collect decent loot, which I can then sell to vendors, or should I approach the game differently, and do other more varied things to boost my cash flow? Thanks a lot for any advice.

have you been to visit the Rapax yet?

Not yet...

well if you want to grind then thats where I would go at that level...

p.s, yes you get a lot of points for doing quests but this isn't a modern game with only one way to go so if you don't want to do the quests or follow any line but your own then thats your choice mate.

Money is easy... do you have anyone with Alchemy? If so brew renewal potions. You need an alchemy of 50 and mix Cure Disease with Heavy Heal and sell it to He'Li

It does train Alchemy, so it offers more than money. Should training be your focus you'd want to mix one at a time.
If your Alchemy is higher money gain is faster as well, because it allows mixing more expensive potions.

Alchemy 15: Light + Medium = Heavy Heal
Alchemy 40: Heavy Heal + Cure Light Condition = Cure Disease
Alchemy 50: Heavy Heal + Cure Disease = Renewal Potion
(there are other recipes but those are the "money maker line")

You can also then cast Identify on the potions and train up mental magic and either divinity or psionics.