It would be really helpfull if somebody could post the details on all the structures available ingame.
Makes it hard to plan when I don't even know what I need to buy or save up for.
Structures are very important, and the key to a good player.
Of course, a level 4 Metal, and Oil are good to have, and what i recommend if you dont have 5000 metal laying around for a Lvl. 5 structure.
Ion cannon, this is a key part in battle situations, you may use it to shoot down enemy Nukes, or severely damage attacking units ( It drops 10 random units health to 1 ).
Nukes, another key aspect. Nukes are usefull in many situations. Have a colony you want to conquer? Well, send a nuke at it all units in their colony will be affected heavily, and some will be vaporized. The same goes for Outposts.
Scanning and Radar jamming capability are also key, Jam radars to prevent your target to see how many ticks away you are from attacking that Op ( Or colony ).
These will be very helpfull structures, and key to success.