How can Iinstall ruby on rails in ubuntu?

I tried to install ruby on rails and I used 'gem install rails', but I got this:

ERROR:  Loading command: install (LoadError)
        cannot load such file -- zlib
ERROR:  While executing gem ... (NoMethodError)
        undefined method `invoke_with_build_args' for nil:NilClass

What am I doing wrong? Or what do I need to do? Can't find help. DO I need to reinstall Ruby? I'm using Ruby2.3 version and ubuntu 16.04. I must say I'm new to ruby on rails, I'm about to learn.

Thanks for your help!