I think the best approach is to get some niche relays in place and simultaneously work on clients that allow browsing these relays specifically.

In the long run we will want relays that do some kind of manual or semi-manual curation of people they allow in, but for the short term since we are so few we could just make some crazy relays as experiments, like a relay that only accepts notes that have content containing sets of 3 specific words in them; or a relay that only accepts notes from people having a key with the first hex-character being the next after the last person who posted (I'm getting crazy); or a relay with an invite policy like lobste.rs -- I don't know.

Once we have this idea out there and apps capable of interacting with relays like that there will be possible for groups of every kind to create relays for them, ban bitcoiners and be happy.