'rails c' command throws back error

On Ubuntu you need libreadline6 and libreadline6-dev, though I don't
know whether that is the same on mint. You might need to remove and
re-install ruby in rvm after installing libreadline so that it
re-compiles with the right options. The full list of stuff I install
before installing rvm is
sudo apt-get install build-essential bison openssl libreadline6
libreadline6-dev curl git-core \
zlib1g zlib1g-dev libssl-dev libyaml-dev libxml2-dev autoconf
libc6-dev ncurses-dev automake \

By the way, when you get an error you don't understand often the best
route is to put the error message into google. I think that would
have taken you to a solution very quickly.