Installing Ruby on Ubuntu 16.04

Install dependencies

sudo apt-get update
sudo apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev nodejs

NOTE for nodejs dependency, you can omit it if its already installed on your home directory (which is a better alternative than installing Node on root directory)
Installing Node on home directory requires Linuxbrew

Using rbenv:
cd
git clone https://github.com/rbenv/rbenv.git ~/.rbenv
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
exec $SHELL

git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
echo 'export PATH="$HOME/.rbenv/plugins/ruby-build/bin:$PATH"' >> ~/.bashrc
exec $SHELL

rbenv install 2.4.0
rbenv global 2.4.0
ruby -v

gem install bundler
rbenv rehash

gem install rails --v 5.0.1
rbenv rehash

Reference:
https://gorails.com/setup/ubuntu/16.04