So, I decided to spend some money from a gift card I got as a gift. I bought the Heroic chest, that has guaranteed 300 gems and 5% chance of heroic. As this is 300 gems for cheaper than the normal shop, I did it.
I already have Commander, but I'll consider recalling to get him to 1 star. A duplicate heroic is definitely better than food!
I spent the rest on my piggy bank (not just to shut it up, lol). The 420 gems I will wait and buy a dragon I want when they are next on sale.