PC Gamer has a free strategy guide up for Galactic Civilizations III: Mercenaries that will help you to "rule the galaxy" in your game.
"Even in the massive sandbox universe of Galactic Civilizations III, there can only be one ultimate supreme leader of the galaxy -- and we think it should be you. We suspect you'll agree.
But it won't be easy. You'll need to muscle, sweet-talk, or buy your way to the top of all the other species vying for control of the universe in the newest installment of this classic 4X franchise. We loved the base game when it came out last year and its newest DLC, Galactic Civilizations III: Mercenaries, builds on top of that rock-solid foundation."
Read the strategy guide here: http://www.pcgamer.com/how-to-rule-the-galaxy-in-galactic-civilizations-iii-mercenaries/