There are three type of in-game resources: two are minable (Gold and Crystal), and the other one (Quantum Dust) is not.
Gold and Crystal are minable and easy to obtain/store: you just need to level up your mines, factory, and storage facilities.
Quantum Dust is not minable, and this makes it rarer.
There are only two ways to obtain it: by force (battle other users and claim your loot) or by wit (trade it for other resources you have a surplus of).
Quantum Dust is the most important resource as it directly determines your score.