Check out Netlify (https://www.netlify.com) for a simpler setup that's also free and lets you use Jekyll plugins, enables very aggressive caching on the CDN level, but with instant cache invalidation and atomic deploys, and brings features like deploy previews (a unique preview URL for any pull request), form processing, redirects, rewrite rules, proxying, etc, etc...
[Disclaimer, I'm one of the founders]