I think I'm gonna go metaphysical here. After all there seemed to be many instances where it was mentioned that the world was created to give Garion a place to stand....... once he showed up that is. so how about the village of gara, and its people existed as a place to produce Garath? after all at the end of the age it went bye-bye. Alorn would be my next closest suggestion. He has an active intelligent mind, that doesn't succumb to impetuous action, so not an Arend (toss in how much they set his teeth on edge) he despises drug use, and not to fond of snakes either, so pretty much rules out Nyissan. He was beaten by a girl's father..... which actually rules out Marag, since they were matriarchial... he'd have been beaten by the girl's mother. who cared who her father was as long as he was good looking and muscular? Tolnedrans? They set his teeth on edge at sixteen for being haughty and materialistic, but they were also his first experience with money, Since Gara had none, that is a second argument against him being Tolnedran. Angarak? not no, but unh-uh, no sacrifices in Gara at all.
Since Belar was a party animal, as well as wanting to be "big brother" instead of ruler over his people, it fits more closely than any other gods' peoples. This does not rule out him being a Dal possibly, but I think he addressed, and ruled out, the possibility of him being a Morind or Karand early on.