I mean, I can certainly see the value in a freebie island.
Maybe have a weeklong event that adds a third currency (like they kind of already do with maze-space events, like the current comic book one). This third currency is abundant, and can be bought. At the same time as the event, make this third currency able to do everything gems can. Give consumers a taste.
Let them buy those dragons (maybe bump up prices the week before so you can knock them down during the event) they've been eyeing for awhile. (You can also get this third currency from the island, the island is basically like an always wins slot machine that recharges every hour or so).
Let them become addicted to the power of this third currency that acted exactly like gems.
Then after a week, take it all away. No more third gems, but you still have your normal gems.
Then, have a 3 day long sale on gems.
Those who became crazed by that power now see an easy and cheap way to experience it again.
Then take a 2 day break.
Then for another day, have the same discounted gems.
Then another 2 day break.
Then another discounted gem sale, but this time it's not as low as it was over the last week.
After this event, you should have a lot more people hooked on Gems, and it would probably do better financially than a Heroic Race.
Okay, so maybe not the best name.
What this does is adds a new building, maybe 200-300 gems worth.
It is a one-building controller for all the farms. You select what you want to grow and all availible farms will grow that exact thing simultaneously. You can also collect from this building.
That's really it. A gem building due to how convenient it is that allows you to grow crops in far less clicks.