This worked in my game. It's more important to pay attention to atmosphere total than percentage as Brian said. These are rough numbers, not sure if every game is slightly different but it probably is. Don't worry about temp until the gas mix is in the ballpark.
Drop CO2 to 0.0
Add
Nitrogen 0.790 atm
Oxygen .200 atm
Argon .013 atm
I tend to add last to adjust temp to final value.
Safe Greenhouse Gases .098 atm
Total Atmospheric Pressure 1.10 Base Temp -48 C Surface Temp 2.79 C Colony Cost 0
Pay attention to colony cost on the Summary screen. As long as it is going down, you're moving in the right direction. You may need to adjust amounts slightly to achieve zero colony cost. Don't expect things to happen overnight especially terraforming. I find that Aurora is not a game for the impatient. I plan for the long term spreading goals over years or decades.
