I keep reading that every faction get different bonus when fighting inside there own culture.
But i cant find out what these bonuses are can anyone tell me(per faction please)
You have to do the research before you get the bonus, but they are. Without the research culture will just increase your own planet's allegiance and decrease that of enemy planets.
A. TEC - Antimatter Regeneration
B. Advent - Shield Mitigation (not migration).
-Advent Rebels can also get a bonus to shield regeneration.
-Advent Loyalists can get other bonuses like weapons damage.
C. Vasari - Weapon Damage
B:your bonus.
I believe you always get your bonus if fighting in friendly culture.