When it was working earlier this year, I ran level 7 and 8 (the missions with little islands with caterpillars) and the drops weren't great, but in general you got 1 per flower gem or better and occasionally a 4*. I just passed through 6 so I really cant comment on what it did.
I will try the next one but if its more than a couple gems per it will be better to run the trial of strength where you get some ampy and birds to sell,
and I will never have enough LC just like now.