Since the update with gyms not that long ago it seems like the gyms mess up a lot between "Errors" and cant take over the gyms that you defeat. The gyms needs updating and have an option for multiple people taking over a gym at one (that seems to cause the gyms to mess up right now).
Also it would be great to get more chances at coins. Like more time you get for protecting a gym the more coins you get in the future (it will be max 50 coins but after you stay in the gyms for X-amount of time the coin value would increase by 10 or 15 coins). Same with taking over a gym except it stays the same for each gym battle (i.e. 5 coins for 1 person in a gym and goes to 45 coins if 6 people are in the gym). And maybe find coins at Poke stops which will be uncommon to find but you get max 5 coins.
my Mustang about Pokémon GO, v1.37.2