Installing Ruby on Debian 8

$ sudo apt-get install -y build-essential zlib1g-dev libssl-dev libreadline-dev libgdbm-dev openssl

$ mkdir ruby
$ cd ruby

ruby$ wget https://cache.ruby-lang.org/pub/ruby/2.3/ruby-2.3.0.tar.gz
ruby$ tar xvfz ruby-2.3.0.tar.gz
ruby$ cd ruby-2.3.0

ruby/ruby-2.3.0$ ./configure
ruby/ruby-2.3.0$ make
ruby/ruby-2.3.0$ sudo make install

$ ruby -v
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]