So a little advice then..
1) Resources, especially Elerium are generally rare. Ok, not entirely true, the red, which is Durantium, is extremely common. So generally, your common ships that would always want to be able to build, should be designed without using any of these resources. Its perfectly viable to play and win without ever using a resource on a ship, but obviously, who doesn't want cooler ships?
2) Resources can also be used for special buildings on planets.
3) Resources in GC3 are very different than most games. You don't need them, you don't continually create more of them over time, and if you use them, and then kill/scrap your ship/building you get them recycled back to you. You can unlock higher amounts of the resources you mine via tech.
4) Therefore, the real resources that you rely on and actually use to build things or acheive goals are:
Research Output (for tech)
Manufacturing (For building ships quicker or buildings)
Culture (For expanding the space you influence and eventually planet flipping)
Credits/Wealth (Because there are maintenance costs to everything)
Hope this helps a little!