Where can I easily get minerals?

You're short on minerals for building upgrades. Besides mining, check quest rewards, event participation, and shop exchanges. Efficient resource management is key, so be thorough, hmm!

The fastest way is to pay. Otherwise, as the person above mentioned, actively utilize things like gathering, missions, the general store, and the kingdom shop! Gathering is important. ^^

^-^ It seems like Dr. Em requires both time and effort in strategy. I hope you can work hard with your kingdom members~~ It's also quite rewarding to exchange for gem boxes in the Duel Arena shop. ^^ Although it might change again after redeployment, I recommend the center for gathering. You can acquire more resources relative to the time spent!!