Gives you +5 population so when you run out of population just build one of these.
Research Labs
Allows the research of new technologies. Also the more Labs the faster the research is, and if paired with a research commander its even faster. Make use of these on Toxic, Radioactive and also Tundra as these are prime Research planets.
Solar Plant
If in position 1, use these and skip fusion reactors as it will give you the same amount of energy as the fusion reactor. Also note that the amount of energy is determined by the x amount of solar resource the planet has.
Antimatter Plant
Derb any other type of energy plant on the planet and replace them with this as it gives you +10 energy on the planet.
Multi-Level Platform
Gives you +10 area. Cost a fortune to build.
Orbital Base
Gives you +10 population to continue to build your bases.
Gas Plant
Gives you the amount of energy as the planets gas output is. If you are on a radioactive or toxic planet, skip the Fusion Reactors and use these, due to giving you a +4 gas resource and its much cheaper. But when you have Antimatter, derb these and use the Antimatter.
Fusion Reactor
Gives you a base energy of +4, no matter what planet your on.
Terraform
Out of space on your planet, don't want to derb some precious structures. Then use this as it will give you +5 area on the base. Its very useful and very efficient. Its big brother the Multi-Level Platform.
Biosphere Modification
Basically what this does, is it makes a toxic planet or any type like this more fertile.