Issue in install old Ruby Gems

Question

I am trying to install ruby gems and having the following issue. Please suggest. I am a novice in Ruby n Rails. Right now I am using Ruby 2.0.0.

Bundler could not find compatible versions for gem "nokogiri":
  In Gemfile:
    nokogiri (~> 1.5)

    fog (~> 1.23.0) was resolved to 1.23.0, which depends on
      nokogiri (~> 1.5, >= 1.5.11)

Bundler could not find compatible versions for gem "ruby":
  In Gemfile:
    ruby (~> 2.0.0.0)

    nokogiri (~> 1.5) was resolved to 1.8.5, which depends on
      ruby (>= 2.1.0)

Bundler could not find compatible versions for gem "sprockets":
  In Gemfile:
    activeadmin-wysihtml5 was resolved to 1.0.0, which depends on
      activeadmin-dragonfly was resolved to 0.0.2, which depends on
        activeadmin was resolved to 2.0.0.alpha, which depends on
          sprockets (>= 3.0, < 4.1)

    sass-rails (~> 4.0.3) was resolved to 4.0.3, which depends on
      sprockets (~> 2.8, <= 2.11.0)

Answer 1

As the most easy solution I'd propose to remove versions from Gemfile ie instead of writing

gem 'nokogiri', '~> 1.5'

use just

gem 'nokogiri'

The same for all conflicting gems. And then try to rerun you bundle install . This would make Bundler more broad possibilities to find suitable versions. After all dependencies are installed correctly, just fix gem versions according to Gemfile.lock