Farming herbs is best used when combined with other methods. Kingdom is also a very good passive moneymaker. Unfortunately at those levels, most of your methods for making money will be slow. If you do the keldagrim questline, I've found that the chaos dwarf battlefield can make quite a bit of money if you hunt the cannoneers the right way, the trick I use is killing dwogres until the aggression period is over, then you can safely attack the cannoneers without getting piled. If you've done the chosen commander, killing the statues in the bandos throne room can be quite good for lower levels. For someone who gets bored easily, or doesn't want to camp monsters, try pickpocketing HAM members and doing the level 1 clue scrolls. This may seem slow, but it really does make quite a bit of money due to how fast you can do level 1 clues, and the fact that some of the rewards can be worth quite a bit. Hope that helps.