Step 1: Upgrade Packages 
# yum update
# yum groupinstall "Development Tools"

Step 2: Installing Recommended Packages
# yum install gcc-c++ patch readline readline-devel zlib zlib-devel 
# yum install libyaml-devel libffi-devel openssl-devel make 
# yum install bzip2 autoconf automake libtool bison iconv-devel

Step 3: Install RVM ( Ruby Version Manager ) 
curl -L get.rvm.io | bash -s stable

Step 4: Setup RVM Environment 
source /etc/profile.d/rvm.sh

Step 5: Install Required Ruby Version
# rvm install 1.9.3

Step 6: Install Another Version ( if Required ) 
# rvm install 1.8.6

Step 7: Setup Default Ruby Version
rvm use 1.9.3 --default 

Step 8: Check Current Ruby Version 
# ruby --version


Update rubygems
$ gem update --system
$ gem install bundler
#Test ruby and rubygems are working
#Close shell and reopen for changes to take effect
$ruby -v
$gem --version
# Rails
$ yum install sqlite-devel
$ gem install rails
$ gem install sqlite3