Divinity in a New World

I tend to start with an established pantheon rather than start from scratch. I like reskinning deities from other settings and then adding my own. I also lean towards only fleshing out the deities necessary at the time. So if there is a cleric then they definitely get some live, and depending on the back story of characters and NPCs I build others.

this sounds like the plot of a couple of final fantasy games

I currently run with the usual gods, but I will be open about PC's attaining divine status if they become great enough.

I've been playing it fast and loose with my current campaign as far as pantheons. I've set up a few religions, Elvish priests of light, Human Pelor worshipers (not the same thing in my world), cults of Dragonborn worshiping Tiamat and Bahamut. But I have not solidified an actual pantheon. I did this partly out of laziness and partly to keep my options open. This is a homebrew setting that I am sort of building on the fly as we campaign.

I toyed with creating a pantheon based off the Sumerian pantheon. I even found an article out of an old issue of Dragon magazine that had done a D&D conversion. The problem I ran into is that the Sumerian gods represent so many different things. For example, Enki, depending on which story you listen to, is the god of Water, Trickery, Cleverness, Royalty, Rule of Law and Societal Order. I disagreeded with almost all of the calls made in the conversion article, and setting alignment for these deities is next to impossible. I believe that this is likely due to cultural associations. The Sumerians lived in a world so vastly different from ours, that we cannot understand the associations they made with various concepts that were then deified. I tend to think about religion in this way: what does a religion express about the cultural mores and norms of its worshipers?

I've realized that I will need to set up some religions for my next campaign. But I'm not going to do the pseudo-Greek/Godsfall thing; starting from the gods as a screwed up extended family with superpowers living in an alternate plane. Instead, I'll start with cultures and ask: what is this culture like and what sort of god/gods fit with that culture (I plan on having several distinct human cultures, as well as the cultures of the other races).

Not really, although there is a racial divide.

In my world, someone/something can be worshiped as a god, but not be a god at all. Conversely, actual otherworldly beings could be worshiped as gods, but it looks no different than a "Golden Calf" religion on paper. Faith is the fuel for divine power. So Clerics worshiping the hypothetical "Golden Calf", if their faith is strong, will have just as much power as Clerics worshiping Kord, or Bahamut, or Satan , or Demogorgon.

As far as the priest of light divide, the Elves are an ancient monastic order that follows a teaching in which light itself, and all the concepts they associate with it, is worshiped. Humans anthropomorphise light into a god; Pelor. So, rather than there being two distinct gods representing the same thing but for different races, there are two distinct religions worshiping similar concepts under different names. In general, the Elves would view the Pelor worshipers with disdain and pity; seeing a misguided attempt to worship light. The Human Pelor worshipers would view the Elvish religion with either awe and brotherhood, or angry denial; they might consider them a sort of "father-order" religion, or as heretics.

A quick breakdown of of racial/cultural religions:

Humans: As usual, diversity. Humans have many religions which flourish in different areas and cultures.

Dragonborn: Worship Tiamat and Bahamut as the two sides of the coin of war. Tiamat is the chaos of battle; the frenzy, the bloodlust, the unpredictable outcome. Bahamut is discipline, order, respect for command, the well executed plan. However, a new priesthood has arisen and is changing the landscape of this loose religion and making it more cultish.

Elves: High Elves are rare and reclusive. They mostly live in secluded enclaves and monasteries far from other races and inhabited places. They worship pure concepts such as Light, Life, or Knowledge. They are the longest lived of the races and consider themselves the stewards of history and life. There are no Wood Elves (so far) in my world. There are Desert Elves though. They live as a sort of Bedouin analog; they are wandering people of the desert. Their religion is monotheistic and vague; they worship the wholeness of creation. Their religion is big and vague, because they spend a lot of their lives striving to survive in a desert waste. They are tough and practical, and their distant, disinterested view of god is indicative of a central philosophy of theirs: We make our own way in the wide world.

Halflings: Two distinct varieties of halfling exist: Joking called Wildlings and Houselings. Houselings are similar to Toleinian Hobbits; they like comfort and ease. They are farmers, shepherds, millers, carpenters and innkeepers. It is rare for an adventurer to come from this stock. Their religion is pastoral in flavor; they worship a sort of "Fat Buddha" smiling god of plenty (this is vague right now, because we don't have any halfling players and we haven't gone to the part of the world where they live). The Wildlings are tribal savages. They live in treehouse communities deep in a vast secluded forest. Their religion is animist in flavor.

Dwarves: Dwarves believe they are descended from one being whose name translates to "First Stone". They believe this being fell to earth as a meteorite and forged the Dwarven people from the stone of the earth. Thus, they are ancestor worshipers. Clan and heritage is very important to every dwarf. Currently, their culture is divided and scattered among the northern mountains. They lost their homeland in the great Catastrophe that reshaped the world. Thus, they lost all the records of their heritage and history; the most important things in their culture! The search for the dwarven homeland is a driving force for their culture; as well as restoring the royal line, believed to be descended from First Stone.

Half Orcs: There is no central half-orc culture. They are rare and almost always the product of the ravishes of war. The orcs control an island nation to the south and are notorious as raiders, reavers, and pirates. Particularly along the southern coasts.

Half Elves: Half-Elves are extremely rare. Elves rarely mingle willingly with other peoples.

Sorry, things got a bit far from the central question of pantheons. But like I said, this is how I think of religions: as an expression of culture.

Fickle humans.
All of these are amazing! I especially like the desert elves, I feel as if the desert is an underplayed environment. And the mentality from race to race is both insightful and intriguing, I might reference back to this every time I am building a game around a certain culture.