If you need approx 50 crates for the Hunter, that's 5x12,500 = 62,500 coins, I think, if you buy them 10 at a time.
One of those challenges is 350, so that's about 178 of them.
How fast are you guys completing these challenges approximately? Are they all stacking up so you can do 6 at once? I guess my real question is: does it look like you are on-track for getting enough?