To be honest, I've not actually put any thought into my religion at all
(just like real life). I've just been grabbing names off the
wikipedia list of Maya gods whenever it seemed appropriate. I guess I imagine that the religion would be something appropriate for society with a distinct lack of attention span, a huge propensity for theft, and a fairly laissez-faire attitude about murdering other species?
I could take a stab at some tenets though. Like:
1: There are a whole ton of gods, pretty much a god for any occasion. If you need to know the god to pray to in a situation feel free to come find me!
2: The world and everything in it were created by gods or devils (which are just gods that the other gods don't like, and are different from the demon that lead the evil crusade)
3: Gods take a active role the world, causing most things to happen. Good things happening mean a god is pleased with you, bad things happening means a god is angry or a devil has taken notice. Which leads to the most important tenet:
4: The point of the religion is to please the gods and hide from/drive away the devil. Most gods are pleased/angered by you doing what they like/dislike, like the god of war likes war, the god of life dislikes war.
5: Since it's totally impossible to please all the contradictory gods it's the shamans job to intervene, making sure the tribe is striking a balance between the gods, or using rituals and sacrifice to make the angry gods happy or to ask a specific god to intervene in a event. (That is also how some magic works. Other magic is just straight up blessings given to a person or group of people by a god/devil for whatever obscure reason they have.)
6: Gods are not invincible or infallible, although the more powerful ones when acting within their own sphere can seem that way. But especially when they take a mortal form (which they sometimes do as some type of mortal or animal or demon or mega beast). And occasionally a god can die or a new one can be born/raised up/appear. This is a very rare event though, and normally only the most important and powerful shamans will be aware of it at first.
Um. Those are some pretty generic tenets. I'm not sure if that was what you were looking for. Or if you were looking for specific important behaviors to observe or how the religion wants to organize society. I'm sure there are plenty of important rituals to observe and rules to follow, but I don't know if they are worth trying to make up a bunch right away. If you wanta have the goblins sacrifice people for various reasons, that might be appropriate. Although sacrificing people not in the tribe might be the most appropriate, given the general Kea lifestyle.