Unlike WordPress, a blog powered by Ghost rarely needs to have its page created on-the-fly. The main reason for this is comments: it's much harder to cache pages (at a reverse proxy level) when the pages are (partially) user-generated. .
Therefore, I've found the following CloudFlare page rules result in not only an increase in performance, but an increase in reliability of my blog:
/api/*: cache: bypass cache, always online: off. (This is important for the Ghost admin panel.)
*: cache: cache everything, edge: 1 day, browser: 4 hours, always online: on.