with old school starcraft in mind . you could use science vessels to search for minable planets or recon ships to show cloaked vessels. heavy battle ship, light attack ship. leveling technology(build this research facility to gain this ability for x location/planet).
ohhh depending on how in depth you wanna go on the planets lol you could set it up so you could land on an inhabited planet and setup shop for your own comunity and try to take the planet over once you think you have enough forces built..