Well, I got all seven mounts I didn't have from about 25 crates.Trick is picking the crates to make sure you choose ones with mounts that only drop from that crate first, as if another mount can drop from it you might get it on the way. Once you learn a mount it won't drop again.
This post was from a user who has deleted their account.
My luck is on killing spree..spent 1300+ dubloons and get 0 mounts.. :D