Instead of trying to specifically carve out spaces for each one, try just figuring out the balance of the starting play area and immediate neighboring regions. Then have rough ideas of where some other continents in the world are, and as other spieces come up that are rare for the region you can say they are originally from continent X.
Until the players actually go visit these other places, you don’t need to have societies fully formed and figured out. Once players decide to visit, you should have at least one session of sea/air/whatever travel buffer to give you time to populate new lands (and can then adjust for any storyline/player interest.)
For example, in my campaign I told my players that the elven homeland was in the continent to the south. Three years later they are finally going to visit there, and it turns out I now know that the elders and majority of elves in the capital city live in a giant treetop metropolis while halflings and some other races are engaged in a 1920s style drug-fueled gang warfare on the ground level amidst a technological revolution (Drive-by violence is much more interesting with repeating crossbows and fireballs instead of tommy guns and bombs). The elves care very little about what the “dirty ground races” are up to because as a consequence of their longevity, they are very slow to change and adapt to a changing world.
Had I tried to figure out their society at the start of the campaign, it would have been nothing like that.
~Phasers and molasses,~
~Phasers and molasses!~
~If you want some, just ask us,~
~We’ve got phasers and molasses.~