If you do absolutely everything the current cap is 45 coins. I said I skipped a lot of that. Yes I spent under 2 hours and all I did was the weeklies in the anniversary area. I also did the two weeklies in Dorne and killed the weekly world boss.
When all was said and done I had 35 coins obviously you can do more that takes a lot more time but I did it in a way that took the least amount of time possible. I threw it up as an example that you can get a decent amount of coins without spending a lot of time
I work smarter not harder.