The number of feathers it takes to get to level 7 is 1,600. Since my birds just leveled up I am a long, long, loooooong way from leveling up again. I am not about to burn 80 gems on the treasure chest because I have no idea what I will get, maybe two blizzards like some others. Maybe a chili like I get when beating the Daily Challenge. Not worth the risk. Today I burned 60 gems to finish off the boss in the DC and it paid off with 250 feathers for silver, my last bird to level up.
As for the arena and not getting decent matches, I have found that patience pays off. I will restart the app as many times as it takes to get a decent opponent. Last week my margin of victory was crazy. This week I have been more patient and my margin of lead is insane, I have lost only a handful of rounds. I am ahead of 2nd place by more stars than 2nd place has in total just by being very selective and patient. Having experience from finishing the 560 levels and knowing how to best beat the arena levels doesn’t hurt at all.
Thing is that it isn’t skill, it is repetition and memory, with a little luck not coming across one of the immortals. Those micro-pigs that survive just about anything and everything. And if on the chance of encountering one of the immortals, having just the right bird in the selection to get at it.