create ctags for all your gems using Gemfile.lock

create_ctags_with_bundler.rb

#!/usr/bin/ruby
require 'bundler'

lockfile_contents = Bundler.read_file('Gemfile.lock')
lockfile = Bundler::LockfileParser.new(lockfile_contents)
paths = lockfile.specs.collect do |spec|
  spec.__materialize__
  spec.full_gem_path
end

system("ctags --extra=+f -R * #{paths.join('/* ') + '/*'}")

Thanks for posting this !