How to jailbreak my iPhone 5c with iOS 8.3?
Solution 1:
At the time of writing, there is no public jailbreak for iOS 8.3.
Solution 2:
I'm not entirely familiar with the technicalities of how this works, but Clash of Clans has an extra payment verification system, as do many popular games, that prevent the conventional in-app purchase bypass from working. You will not be able to get free gems/coins/etc. on Clash of Clans simply by jailbreaking your phone.