16.04: Unable to install compass

this ubuntu version brings ruby 2.3.1p112 (2016-04-26) [x86_64-linux-gnu]. so all i did to install was the normal process which is gem install compass but this installation throws this error:

Building native extensions.  This could take a while...
ERROR:  Error installing compass:
    ERROR: Failed to build gem native extension.

    current directory: /var/lib/gems/2.3.0/gems/ffi-1.9.14/ext/ffi_c
/usr/bin/ruby2.3 -r ./siteconf20160907-12074-v2oz2d.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.3.0/gems/ffi-1.9.14 for inspection.
Results logged to /var/lib/gems/2.3.0/extensions/x86_64-linux/2.3.0/ffi-1.9.14/gem_make.out

i tried with installing ruby-dev with the command apt get install ruby-dev as root but it is not available on this ubuntu for some reason, it throws this error:

Package ruby-dev is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'ruby-dev' has no installation candidate

The compass install is failing because of the lack of the ruby-dev installation.

ruby-dev is included in Ubuntu's repository. You'll have to update your repository to have the full available packages and depends.

Perform these commands to do this:

$ sudo apt update
$ sudo apt upgrade
$ sudo apt full-upgrade
$ sudo apt install ruby-dev