Cannot install Gem?

Sorry, newbie here. I am on Linux Mint 64 bit 17.3. I used ruby-install
to install Ruby 2.3.0 but cannot install gem? It doesnt seem like I can
run Ruby either?

My terminal says

Successfully installed ruby 2.3.0 into /home/user/.rubies/ruby-2.3.0

However when I then
$ gem env
The program ‘gem’ can be found in the following packages:

  • ruby
  • rubygems
    Try: sudo apt-get install

~ $ gem list
The program ‘gem’ can be found in the following packages:

  • ruby
  • rubygems
    Try: sudo apt-get install

Do I need to cd to a certain directory to run the above? I tried
~/.rubies to no avail.