The Civilizations

Here we try to find which will be the civilizations which will exists in the Middle Earth.

For the Moment I see :
Western Humans
Easterlings & Haradrhim (if someone has one world tos peak about both of them except "bad guys" ^^
Elves
Dwarves
Hobbits
Orcs
Creatures
Valars and Maïas

Creatures encompass spiders, goblins, giants and other small and large creatures?

Yep all creatures, in my opinion those who are not able to build different buildings (to the maximum they can build their Lair, even a Castor can do that so not really a kind of intelligence) . So even if an Ent is an intelligent creature, they will be in the creature civilization because they will not have a technological development, indeed like trolls, spiders (which will be their cultures).

Goblins are orcs and so will be in their Civilization with Uruk Hai too.

Shouldn't there be seperate cultures within the culture group? Such as Gondorian, Rohirric, etc. Or atleast Dunedain, Variag, etc.?

Yes the Civilization Human is seperated between the different kinds of humans like rohirrim, gondorian ... But that must be discuted in a Culture topic