Some other points, adding N2 is really only needed if you need to lower the oxygen % and already have a good temperature.
I also find it helpful to concentrate on temperature first if your colony cost is over 2.0 for temp, as the improved temperature will immediately reduce colony cost. Once you get to 2.0 colony cost, then add the 0.1 atm oxygen (this will have a slight heating effect). Then add greenhouse gases (I use CO2 but that's just cosmetic), anti-greenhouse gas (if you need to cool) or N2 once your temp is in range to pull O2 concentrations below the max 30%. Keep going after that if you still need to cool/heat some more. If you need so much heating cooling effect that O2 drops back below 10% then you will need to add a touch more O2, but I haven't needed to do this yet.
I have't bothered trying to terraform a hot/high pressure system yet, as it seems rare to find one that isn't a too much trouble. Obviously poison gases should be eliminated if they are present, just be cognizant that some poison gases (like methane) are also green house gases, so if you start eliminating methane on a cold planet, you colony cost will actually go up until you are done, so you want to keep an eye on that by either terraforming prior to serious population is added, or shifting some additional infrastructure to offset.
I am also a big fan of platforms/ships over installations. The pop requirements for the installations are high, and I prefer keeping me struggling colonist work force focused on building mines/factories in the early days. Not only do platforms/ships have no work force requirements, but their officers can provide bonuses, which I think double stack with the local administrator terraforming bonus if I am reading the screens correctly. Facilities are also a stone bitch to move after you are done since they are so big. Personally, I use platforms with tugs to push them around. The micromanagement of using tugs to move 10 or platforms when you are done with a project kinda sucks, but it seems to me to be the most cost effective way to build the capacity. Since projects take so long, major shifts in platforms (other than ferrying new construction to project sites) is fairly infrequent. If you want simple, then use ships, when done, just order the terraforming TG to go to the next project.