Somethings to consider, when thinking about race moves. Including a race in a class says some powerful stuff about both the race itself (Orcs have Fighters, obviously, but do they also have Rangers? Do they have Wizards? What do these things tell us about Orcs in the world?) and about the class, too. From a setting standpoint, it's important to understand first how that impacts the world - what it says about Clerics in general that humans and dwarves can take up that role but nobody else can. Does that mean Elves have no gods? Does it mean halflings are spiritual but not religious? Why are humans the only Paladins? etc etc. It's not an arbitrary choice but a setting statement.
From a mechanical standpoint, the race moves do one of three things - illustrate skill (giving an easier chance to successfully accomplish a particular task) illustrate difference (breaking the rules by allowing stuff like rolling with a different stat, using cleric spells when you're a wizard, etc) or illustrate options (broadening an existing move to encompass new options at various levels - new questions for Discern Realities, etc etc).
Often, the mechanism is the last thing we'll come up with when determining a race move. Remember that the race moves (plus any race-related tags for equipment or whatever) are the only way, before the game begins, that players can learn about the races of the game. They need to paint a broad, interesting picture you can start from.