Althouuugh I think that training nowadays isss useless.. to make the most of the time invested, I would farm smal stones at the same time that I farm charm points so I would go to these places, one after other when I'm done with its bestiary:
- Goblins of femor hills/edron cave: As Trululu said this is the easiest placce to loot them.
- Sibangs in the Ape city loot thousand of them asswell
- Stone Golem
- Pooka, twisted pooka, faun and dark fauns: drop them asswell but with a smaller probability (but they give better loot and exp, so you would compensate the less amount looted with the prob of buying the rest in market.
Hope I could help.