Ancient Coins are a main form of currency in the game to get items from shops such as Borgen, player shops, the Mat / Booster Shop, and can be used to get special emblems.

HOW TO GET AC

There are quite a few ways, most of which are free.

FREE METHODS
-Defeating regular enemies (0.5% Drop Rate) or Titans (5% Drop Rate)
-Daily Quests (Can get 10-15 AC daily)
-Monthly Rewards (Scroll down on the Daily page - Can get you 800-2000 every month)
-Your own Shop (Initial start up cost and sales are taxed) Can be a decent source of AC dependent on items listed and DR level.
-Clan Control (Every 6th, 7th and 8th)
-FSHM
-Rotating Events include AC rewards. Normally every other week and around holidays.

NON-FREE METHODS
-Buying AC - NOTE: $25 of AC gets you custom emblem uploads, $100 gets you a permanent subscription to the game, and $200 gets you a perma sub to gift to someone else. - Currently only available via iOS, no PayPal. (NOTE - On Android, PC, buying AC is unavailable.)
-On the first of every month, you can get 250 AC. NOTE - THIS REQUIRES AN ACTIVE (or Permanent) SUBSCRIPTION

ADDITIONAL NOTE:
On occasion players will gift you AC for whatever reason. Sometimes it's anonymous. It's always polite to say thanks on Global Chat.

Also, it's considered bad form to beg for AC in Global Chat. There's even a Code of Conduct rule against it. Be patient, the AC gods shall bless you!