The following works for me using Refinery 3.0.6.
$ ruby -v
# ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-linux]
$ rails -v
# Rails 4.2.10
$ gem install refinerycms -v 3.0.6
$ refinerycms _3.0.6_ myblog
Now update your Gemfile to include ...
$ cd myblog
$ bundle install
I then followed the remaining installation instructions
$ rails generate refinery:blog
$ rake db:migrate
$ rake db:seed
$ rails server
I hope that helps.