Error While Installing Ruby

I think you didn't installed the rvm requirements .
Install the requirements like libreadline6-dev , libyaml-dev , libgdbm-dev ,etc..
I think This will solve the Problem.

Install all these with the command

sudo apt-get install build-essential openssl libreadline6 libreadline6-dev \
curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-dev sqlite3 \
libxml2-dev libxslt-dev autoconf libc6-dev ncurses-dev automake libtool bison  \
subversion pkg-config  

Or, Just refer this link.

This instructions are old, following rvm installation instructions:

\curl -#L  | bash -s stable --autolibs=4 --ruby

It will:

1. Download and install RVM
2. Enable automatic requirements installation
3. Install ruby including all required dependencies

which OS you using ?
if you using Ubuntu, then use the link :

if you are using windows
then problem while installing in some gem dependence like. 'libffi-dev', less-rail

than used other OS that very well for "Ruby on Rails" like Linux/Ubuntu

If you're using ubuntu, the copy and paste . You might need to hit enter at some point.

this worked for me.

WARNING: The following packages cannot be authenticated!

    apt-get clean            # Remove cached packages
    cd /var/lib/apt 
    mv lists lists.old       # Backup mirror info
    mkdir -p lists/partial   # Recreate directory structure
    apt-get clean
    apt-get update           # Fetch mirror info