Ruby Rails latst version not being used
<p>I am doing the Ruby on Rails 4 essential training with Kevin Skoglund. I installed Xcode and Homebrew no problems, was following along just fine when I went to do the command rbenv global 2.3.0 to change to the newest version, it won't do it. I was instructed to logout and back in, i shut down and restarted and I am still in version 2.0. How do I get it to change? I am a super noob, but I am brave. I would love to figure this out so i can get started.Also, i went to update my gems and this happened, </p>

<p>ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
So I was stopped dead in my tracks, any help will be much appreciated </p>