First let's update everything I am running all commands as sudo but you run with the level you want
sudo apt-get update -y && sudo apt-get upgrade -y
Now let's install Ruby
sudo apt install ruby
Check if Ruby was installed
ruby -v
Update your gems
sudo gem update
Install bundler
sudo gem install bundler
And install some dependencies like ruby-dev
sudo apt-get install ruby-dev build-essential dh-autoreconf
And finally install Jekyll
sudo gem install jekyll
Check if Jekyll is installed correctly
jekyll -v
If you get a version back, all is good Now if you want to create a new blog you can run
jekyll new myblog
if you are already with the blog folder opened you can start the server
bundle exec jekyll serve