It is worth remembering how common lay membership is. In my adventuring party, one character – an initiate of Orlanth Thunderous and the Sun Dragon – is also lay member of Storm Bull, Humakt, and Issaries. But he has his limits – he refused to participate in Argan Argar worship as a lay member.
For example, in the Lunar Empire, almost every free person is a lay member of the Red Emperor. In fact, many Pelorian cults include worship of the Red Emperor simply as a matter of routine. Of course, you don’t get much for that worship in the sense of magic or skill training, but you do get the benefits of being ruled by the Red Emperor!
Humakt is a popular cult for lay members. Pretty much every full time warrior in Sartar is a lay member of Humakt – he is the God of War after all. But far fewer people initiate into the cult.
Orlanth Rex Lay Member
Any initiate of Orlanth, Ernalda, or another Lightbringer cult may become a lay member of Orlanth Rex. A lay member must give an appropriate gift to an Orlanth Rex initiate, traditionally “a brave sword in battle, a praise song, or loyalty freely given.” The lay member swears to uphold the virtues and justice of Orlanth. The lay member must sacrifice 1 magic point on Orlanth Rex holy days and is expected to attend tribal assemblies.
Where the cult is present, people that hold leadership positions in their clan must typically become lay members of Orlanth Rex. For example, one must be a lay member of Orlanth Rex to be a candidate for clan chief.
There is no Ernalda Regina cult. it is just Ernalda. She’s got enough going on as it is!
Does Ernalda offer the same kind of special Rune Magic to high Priestesses as Orlanth Rex offer to his Priests? No. Orlanth Rex is a historical product of the need for tribal kings to be able to reign priests in. A similar development did not happen with the Ernalda cult in Esrolia.