I see this done effectively by arranging a scene in which the relative mythology can be conveyed.
Imagine everyone raising their glass and shouting "l'chaim!"
You may or may not have an earthly clue what's going on. Does this exclamation mean, "to the battle!" or "to life!" or "bottom's up!" or something else entirely?
The 'show' of the action will convey to the reader the importance of the ritualistic tradition. However. Placing a goy in the scene, who is unsure if they should raise their glass or not, allows someone in-the-know to explain what 'l'chaim' actually means and when it is appropriately used and perhaps the history and relevance. In addition, it allows you to establish a relationship between these two characters.
So. You can build your world and characters by leaning into the Three Fingers:
"Three fingers, what is that? An emphatic 'fuck you?'"
She looked at him in horror. "The three fingers trace to our earliest days. The first finger is birth, guided by Gersaina, the goddess of all that is. The second finger is the mortal coil, when the goddess retreats, an absent mother, and allows us to fall on our own. The third finger is the most important of all, the time when we approach death. We choose either to return to Gersaina for another cycle, or we abandon her to endure eternal torment. The three fingers is our most sacred gesture. It is choice and destiny. There is nothing irreverent about it."