I thought it might help the grind if we were able to convert let gems into coins at a rate of 12 Gems = 1,000 Coins.
This would make it so once you have all heros and your daily login is 120 Gems/day, you could* trade them for 12,000 coins to help speed up the grind for legendary gear.
I feel as though this is balanced, as:
#1. You would have to unlock all hero’s to be able to reach that point
2#. You would still have to log in multiple days in a row (with all hero’s unlocked) to receive the maximum benefits (ex: 8-9 days for a legendary chest).
3#. It’s a choice no matter what stage you are at: Do I save my gems for that hero/pet I want, or do I use the coins to purchase better gear for the hero’s I already have
4#. Once you have unlocked all the items purchasable with gems, it would still give them a use later-game.