Hit the Skirineen early and often. Use the money from your oppressive taxing to buy military units, information, and tech from the skirineen. Other races are hit harder by Skirineen scandals, so taking advantage of your morale ability early in the game when other races may not have many military units, intelligence, or tech will put you a step ahead of the competition. Build a culture center or museum early. Keep you people happy.
People are the most important resource and unhappy people cause major problems.
Once you have enough culture to keep people happy, you can tweak the taxes to get as much money from them as possible. Happy people, raise taxes. Unhappy people, lower taxes. Cyth are the simplest race to play. You don't need any culture.