Castle Clash has many types of currency built into the game. Gold and Mana are the two primary types of currency. These two are your cornerstone when it comes to building up your base, as they are used to build and upgrade buildings, and to train troops and research new troops, as well as to buy magic. Gems or Treasure (the game refers to them as both, but they’re the little pinkish purple stones) are the premium currency of the game. Read on to find out how to get more of both!
Build up your base so that it becomes a Gold and Mana autopilot machine. Do this by building more mana mills and gold mines, and then when you reach your limit, start upgrading them for a higher output. Then, upgrade your gold vault and your mana vault so that you can store more gold. Once you reach your limits on all of those, upgrade your Town Hall, so that you can increase your building limits.
When you need quick gold and mana, go battle against other players and raid their bases. Skip out on players who have bases loaded with troops, or (later on) who have more troops than you. Opposing armies and heroes are usually far more dangerous than the defensive towers, so those should be your main lookout. A few battles against other players and you will easily fill up your vaults again.
Conserve your mana and your gold, too. Only upgrade buildings when you really need to (especially if you want to artificially depress your Might level so that you can fight weaker opponents). Also, send in huge, huge armies when you battle, so that they can get the job done quickly, and without too many troop losses. The more you send in, the less troops you will lose except against extremely tough opponents.
Gems (or treasure) can be gotten for free by completing achievements in the missions area (the icon that looks like a Christmas present). Go there to see what you need to do as well as to claim those gems that you have already earned.
Plus, go to the “more events” tab and participate in everything that IGG puts in there, because many of these events can be worth hundreds and hundreds of gems.