Do note that the level up section* is with a Solo Occultist instead of a Conjurer. So, just get enough points in Shaman for a 16/16 Briarthorn and then focus on the Occu side till later on.
The guide also has a budget Conjurer, but that is a level 100 GT link with faction gear.
*Level up section or build diary for Occu is in the Beginner section of the guide, near the end.