I only have the two default retainers, and decided to make on a CNJ, but I would like to make the other something that would be able to get different things so I don't miss out if there's anything they bring back later that's unique to their class.

Is there any difference between DoM and DoW retainers? What about DoL? How do the item pools (for all ventures, or rather, the ones that matter, I guess) change with each class?