This information is based on my experiences in the church I have attended. The material here is probably representative of many Spiritualist churches, but naturally, other churches could differ. I would feel like a fool, or at best a rank amateur in such a place, because I am not a medium.
Spiritualist church is similar.
Natural law is your guide, and mediums bring evidence of the continuity of life on the other side through messages and phenomena. Although mediumship is a noble endeavor involving heavy responsibilities, spiritualists do not worship people who become mediums. Spiritualist church is for everybody. It's not a requirement. Most of the congregation aren't mediums, aren't going to be mediums, and aren't planning on it either.