There are lots of really importent buildings I’m going to start with the Open spot buildings (Excluding HEF, EF, WF)
Base Control (BC), This is needed to recruit commanders, you need a Base Control in EVERY colony if you want to transfer commanders. How many Base Controls you have in a Colony = How mnay commanders at a colony.
Max Level= 10
If you see something pop up saying “target location can’t hold fleet” when transfering an IMPORTANT commander, upgrade your base control or dismiss an unwanted commander.
Research Facility (RF), Is VERY important, each level adds 1 to your total research speed, with a high enough level of these in each colony it turns a 22 hour research to an 8hr one.
Ship Yard (SY), Used to build ships, the higher the level the less time it takes to build your ships.
Commercial Centre (CC), A level 1 CC lets you join a alliance and a lv 3 lets you create one. It also unlocks spots in your colony but since the Colony hub is level 20 now it is less importent.
Colony Hub (Chub) is the centre of your colony, it is the first building you start with and all other buildings in your colony can not level higher then the colony hub level. It is also handy for looking at how your colony uses rescources and the defence fleets of it. It also protects some rescources if you are raided.
Power Station, This should be your primary energy source at 25 power per hour, even though it requires a open spot with a Seismic Stabilizer I can still fit at least one on Leda. While it is more expensive and costs crystals past level 4 it is much better then a Solar Plants.
Detector: Used to detect enemy fleets arriving, gives us ETA, fleet str, player etc. Quite cheap, if I remember correctly 1hr detection time per level.
Store: Used to store resources, max level 20. It can store 5k resources per level.
Aeroponics: A good building as it produces the same amount of food as farms, essential for non fertile planets. However it is very power hungry.
Hydroponics: A cheaper, less time, resource and power consuming building then the aeroponics, however it gives out less then half the food production.
Factory: A goods production building, very power consuming and a pretty average income, also expensive to upgrade. However it does not cost any rescources p/h.
Missile Base: A defence building, how much damage it does depends on what missiles you have built and your colony leaders tactics, can be expensive to run if your constantly having to use it (you have to pay for new missiles.)
Industrial Plant: A Mega goods producer, even though it costs you a decent amount of ore p/h (Ore requirement rises with level)
Lance Base: I have felt the effect of lots of lances bases pounding my fleet. Its not good. This is a very good defence option even though it quickly becomes too crystal expensive for most non-Altairians. How much damage it does depends on you lance tech and governors tactics.
Colony Quarters: This is essential for your to have a 51%< efficiency, it adds to your colonies population which is needed for buildings (about half as much pop is needed as power) Altairians get a bonus +1 max pop cap per level.
Fuel Synthesiser: This is the only way to get fuel on planets without fuel nodes. It costs ore to run similarly to the Industrial Plant Not the best fuel income, but in some cases pretty much the only independent one.
Solar Panels: This is a pretty much pointless structure, it produces 1/5th of the power output of the power station and the only advantage of this building is that it does not require pop and can be built on a rough spot. Ironically its power output will be lowered if there is not enough power for 100% efficiency.
Farm: A great way to produce food, Farms can be found on home colony planets and Leda. They require 1 Pop per level but no power :D.
Mines: Only way to produce ore other then raiding other places, these can be found on all planets, though very rarely on Leda.
Drills: Can be found on Diploe and nodes can be found on Zeus and Jacot. As with all resources found on home planet. A better way to produce fuel then with the synthesiser.
Special Rescources: (Gas refinery for Seekers, Crystal Mine for Altairs and Heavy Metal Mines for UEO) These require research to construct and their spots can only be found on special resource planets. They Will Not produce special resources on their own, but must be built to obtain them from nodes. With each level the increase production of these resources.