Level 1 tenets
5 - Avant Garde: +25% Great Person generation.
1 - Creative Expression: +1 Culture from each Great Work.
4 - Civil Society: Specialists consume only half the normal amount of Food.
2 - Covert Action: Spies have double the chance to successfully rig City-State elections.
3 - Capitalism: +1 Local Happiness per Mint, Bank and Stock Exchange.
1 - Economic Union: +3 Gold from each Trade Route with other Freedom Civilizations.
3 - Universal Healthcare: +1 Local Happiness from each National Wonder.
Level 2 tenets
5* - Volunteer Army: 6 units are maintenance-free. Receive 6 Foreign Legion units immediately.
3 - Urbanization: +1 Local Happiness per Water Mill, Aqueduct and Hospital.
2 - Their Finest Hour: City Ranged Combat Strength increased by 33%.
5* - Universal Suffrage: Unhappiness from Specialists is halved. Golden Ages last 50% longer.
1 - New Deal: Great Person improvements provide +4 value of the appropriate yield.
3 - Arsenal of Democracy: +15% Production towards Military Units. Gain 15 Influence from each Military Unit gift to City-States.
Level 3 tenets
5* - Media Culture: +34% Tourism from Cities with a Broadcast Tower.
1 - Treaty Organization: Gain 4 more Influence per turn with City-States you have a trade route with.
1* - Space Procurement: May buy Spaceship Parts with Gold.
*
Volunteer army : Best war support tenet from Freedom for multiplayer. These Legions are da bomb when going domination. Get them first and see how they can counter artillery and any other industrial units for a long time. Enough to win the game sometimes.
Media Culture/Universal Suffrage : Best tenets for Cultural Victories. Usually, in cultural games, the culture rate is high so you can get the 3rd tenet in time, combined with Universal Suffrage.
Space Procurement : Order is much more better for science games.
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Other tenets don't need explanation. Overall, if i go for a multiplayer domination victory i will be tempted to go Freedom. Cultural victories as well for both mp and sp. Bad for all other goals.
I gotta say: I think you are seriously underrating Treaty Organization. I felt that way the first few times I played through freedom, but once I actually used it--it is awesome. I've got several city states north of 400 influence right now and I'm rolling in gold to boot.