Here are my most common used gems

Gemfile

# Always
group :development do
  gem 'spring'
  gem 'thin'
  gem 'better_errors'
  gem 'quiet_assets'
  gem 'meta_request'
end

gem 'bcrypt'
gem 'bourbon'
gem 'bootstrap-sass'
gem 'slim'
gem 'slim-rails'
gem 'jquery-turbolinks'
gem 'newrelic_rpm'

# When I need a country select list 
gem 'country_select'

# When I need icons
gem 'font-awesome-rails'

# When I need pagination
gem 'kaminari'

# When I need front-end framework
gem 'ember-rails'
gem 'ember-source'

# When I need Rest Client
gem 'faraday'

# When I need SOAP Client
gem 'savon'

# When I'm using Shelly Cloud
gem 'shelly-dependencies', group: :production