You should disregard the advice from people who are talking about the B100R because it's a very different beast from the B50R. (With one exception: Jimmy is right than on either, the best advice is to just start flat and then tweak as necessary.) For one, the 50 does not have a gain control, so you can't adjust the input level separately from output volume. For another, the 50 is already way loud, and you probably don't want or need to boost the signal going into it (which I agree is often helpful with the 100). For another-another, the 100 has a much deeper voice than the 50, with a lot more bottom-end, so the adjustments you'll need to make to get any particular sound will be very different. For example, I usually find myself slightly boosting the bass and/or low-mids on the 50, but slightly lowering them on the 100.
In the end, though what works for you will depend on what sound you like, in addition to all the usual factors such as the tone and settings of your bass, the surface the amp is sitting on, where the amp is located relative to walls, various characteristics of the room, and so forth.