It worked for me on Android. I had around $14 of google play credit from google surveys, so I did it, but I won’t do it regularly.
I got the LT, which gave me JG, which gave me another LT, which gave me Cyc, who’s already fully covered. Now I need to rush for 14 days to try to get enough ISO to champion him. And there’s no "Sell all 1s" button, so that means I’ll need to sell every single 1 one at a time, so… thanks?
I have major issues updating with the Amazon store as well. I had to kill the whole store and reload to even see the update. Then I had to uninstall reinstall for it to take. The Update button is always there for me but never seems to work.
I don’t have anything else on which to spend the coins, and only recently discovered I could spend them on IAP, so I’m going to throw them at this game before they expire.
For this month I just used Google Rewards money, but I’ll try uninstalling and reinstalling on my amazon device to bring it up to date.