You can take a (one) god or a (one) specialist each turn. If you take one you have to activate it (have cattle for it). After that round you may be not using it again, if you want to.
There are some "misunderstandings" what one use per turn means: The builder and the nomads are passive. You activate them "once" per turn and use them as often as you like (nomads can be used twice with obatala) The rain ceremony and the shaman is active when you pay them and they do their job one time. The herd is also an active one but can be used 3 times (as stated on th card).