Having a blog based on static web pages doesn’t give your visitors the possiblity to react on a blog post. This can be solved by using an external service like Disqus. For non-commercial websites you can subscribe to the plus plan for free. With the plus plan you don’t have to show ads.
The official github pages documentation explains how you can test your Github Pages using Jekyll locally. I had a hard time installing all dependencies. A faster and easier way is to use the docker image provided by Jekyll. Make sure you are using the image with the pages tag: jekyll/jekyll:pages.