Here are the settings I usually have on my game and I think I have it optimized for the most I can get of performance and still have the game looking good!

FXAA: On
MSAA: Off
VSync: Off
Pause Game On Focus Loss: Off
Population Density: Turned Off (all the way down)
Population Variety: Turned Off (all the way down)
Extended Texture Budget: This one depends on your system. Turn it up to the point where your Video Memory is still green.
Texture Quality: Normal
Shader Quality: High
Shadow Quality: Normal
Reflection Quality: High
Reflection MSAA: X2
Water Quality: Normal
Particles Quality: Normal
Grass Quality: Normal
Soft Shadows: Sharp
Post FX: High
Motion Blur Strength: Turned Off (all the way down)
In-Game Depth of Field Effects: Off
Anisotropic Filtering: Off
Ambient Occlusion: Off
Tessellation: Off