I bought the expansion and have been playing a lot over the last few weeks. I finished all the scenarios up to Utopian level (one notch below the highest difficulty) and just won a game on the highest difficulty of the “Red Planet Awaits” scenario. Here’s my typical strategy.
In the early game I like to prioritize getting a synergy of food, energy and science buildings. So that means placing three of each around the same connecting node, then using the “adjacent +1” building on the center node.
When expanding I focus on founding cities in lava tubes due to the comfort of living bonus. I focus mainly on housing+comfort synergies as above for nodes with more than two surrounding connections. If there’s no craters are also okay since they still give a smaller +2 bonus. I only use robots if I need to increase expansion points or if I need to increase the building limit in a city because they don’t give you any support via comfort of living. In the nodes with only 2 or 1 connections I build the non-synergy buildings like atmosphere-increasing buildings, robots, expansion hub and project increase-type buildings.
Once I have a healthy stream of resource income and have surrounding mines built up I start thinking about getting bacteria spreading and also building +heat/oxygen/atmosphere buildings. These are very important even if they are not part of the scenario goal because leveling up these gives you a once-off shot in the arm for support as well as improving your comfort of living bonus. I’ll also be looking to improve the amount of projects proposed and amount of projects you can pick per turn around this time when I have spare science.
You should get a few rovers for exploration + resource gathering. Also, rovers can sometimes save your game when support is running dry - you can focus on the support-giving nodes which can keep you running until the next shot-in-the-arm from +heat/oxygen/atmosphere level. On the higher levels I’m often ALWAYS behind on support but I’m able to build more population and support-giving buildings and stay in the game (sometimes only barely but I make it - these can be the best games!).
The leaders are very situational so I’ll choose the one that I think is good for me depending on the situation.
Trade routes are often useful to top up a laggard resource. You don’t need many early on but as the game goes on you need them for space projects, which can be lucrative. They are also a good way to expand oceans. By end game I’m constantly picking and fulfilling space projects.
Approaching end game you are now at the stage where animal and plant spreaders are useful. Support needs will be growing big, but animal and plant spreading WILL get you from being in the red into being in the green. You should also be able to build some large support-giving buildings to help out. It is about this time that I start to focus on the actual scenario goal and go for the victory.
Later in the game, make sure you don’t build more mines than you need. Your biggest income will need to be energy, food and research. There’s no point building another mine if your income is already 10 - instead use it for a plant or animal spreader, support building or a big +food provider.