My idea: Gem Hunt:
In Gem Hunt you can join a league if you want with an amount of players around your level. (not sure what amount, something like 100)
They all pay an amount of gems to contribute, depending on which league you join.
In small gem hunt you need to pay 100 gems, in medium hunt 500, big hunt 1000. (not sure about this amount either, just something i thought would be a good amount).
All the gems will be put together.
During the Gem Hunt, you can attack the other players in your leagues, to earn points.
1 star = 1 point
2 stars = 2 points
3 stars = 3 points
The amount of points that you have will give you a ranking.
At the end of the Gem Hunt (not sure about the length either) the 1st, 2nd and 3nd in ranking get gems as price.
1st the most of course, 2nd less and 3nd less then 2nd.
All the other players lost their gems.
I think it will be a good change for most people, if you want some more gems and you don't have that much money. It would'nt hurt Supercell because no free gems are given, all the gems rewarded are the gems that were given to contribute.

Hope you like my idea, thanks for reading!