The history regarding the Ebionites and the Nazorean groups should be of great interest, because they represent the best glimpse we got into the earlier core group of jewish folowers of Jesus, led or inspired by James, the Just and the descendants of one of Jesus' brothers, Joses. If we are to understand better what Jesus was and make an educated guess at what were his teachings and his world view, that's where we have to focus.
Although stretching a bit some conclusions, and not an easy reading, I recommend Robert Eisenman's "James, The Brother Of Jesus"; also the excellent work of James D. Tabor: "Paul and Jesus - How The Apostle Transformed Christianity". They should persuade you that the Jesus movement was not about starting a new religion separated from judaism, but it was Paul that took it in that direction.
Eden