I have a question, what is the purpose of the cards you can't exchange for anything?
Also, what do Ion Cubes do?
Cards that can't be exchanged can be collected for one of the Missions in Valeria (0,0) or held in case something is added for it later.
Ion Cubes increase your chances of running into Rebel Drones and provides a 10% increase in Credits gained from each battle for 1 hour when used.