Here is a description of each one of these nations, and the many other smaller nations that you can either ally with or destroy.
URH:
The URH are a group of humans who survived the crisis of global warming and decided to move to other planets for more resources. They now control many systems around the galaxy and are one of the most powerful races in the galaxy
SilverRoid
The SilverRoid are a race of cyborgs led by the most powerful commander in the known universe, Commander Crutoia. Although the SilverRoid don't have as much power as the URH, with Crutoia in command they are a force to be reckoned with.
Epox
An alien race at about the same stage of evolution as us humans, although they have evolved in different parts of evolution more than others. Unfortunately one of those such things is scientific knowledge, because of this they have much more advanced technology at their aid.
Minor Races
Reanor People:
A group of humans deeply connected with the Earth and religion. They have always been neutral, but you could hopefully side them if we give them a good cause...
The Aytoz:
A group of Epox who have separated from their race to watch the birth of stars in nebula around the galaxy. They have become even more scientifically advanced than their main race and although the only side they have ever allied with was the Epox (in the Blatonic wars) they are our trading partners and we could hopefully swing them over, if we get their before the Epox.
Ovrairians:
A group of fully robotic soldiers who were made by the most powerful race in the universe, the Eiolens, to police the universe. Although you do not see them often (or any other Eiolens for that matter) they have sided with other Races before, they would be an extremely powerful in an alliance.
I might add other minor races later on, but this is the main bit of it (the minor races are written in the perspective of the URH empire)