It is my understanding that you get coins for other things besides completing challenges and the Alliance. I do not get any coins other than that. I started a ticket and it got deleted. I didn't delete it. I have not heard a word on anything about it. I'm on ps4, login is Daddio_fx. I'd appreciate someone looking into this. I dont think it's fair for me to have to use real money to get things in game that others can buy with in game cash.
Fairly certain the only way to get coins is from challenges and alliance. Completing all and having a full tier 10 alliance should net you roughly 20-25k per week. Alliance is about 10k, weekly's many are 2k each, dailies vary from 2 embers to 750 coins
There was a brief time when small amounts seemed to come from chests, but haven't seen that since 1.03 at least. That's also assuming it wasn't just from completing a challenge.
If you want to buy all the stuff in the store you need to buy shards. Stuff will be continuously added faster than you can earn coins in game