Here is a rails application with just Bootstrap Sass set up properly

application.scss

    /*
    *= require_self
    */

    // "bootstrap-sprockets" must be imported before "bootstrap" and "bootstrap/variables"
    @import "bootstrap-sprockets";
    @import "bootstrap";

    @import "main";
    @import "about";
    @import "home";

main.scss

Gemfile

    source 'https://rubygems.org'

    # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
    gem 'rails', '4.2.0'
    # Use sqlite3 as the database for Active Record
    gem 'sqlite3'
    # Use SCSS for stylesheets
    gem 'sass-rails', '~> 5.0'
    gem 'bootstrap-sass'
    gem "autoprefixer-rails"

    # Use Uglifier as compressor for JavaScript assets
    gem 'uglifier', '>= 1.3.0'
    # Use CoffeeScript for .coffee assets and views
    gem 'coffee-rails', '~> 4.1.0'
    # See https://github.com/sstephenson/execjs#readme for more supported runtimes
    # gem 'therubyracer', platforms: :ruby

    # Use jquery as the JavaScript library
    gem 'jquery-rails'
    # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
    gem 'turbolinks'
    # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
    gem 'jbuilder', '~> 2.0'
    # bundle exec rake doc:rails generates the API under doc/api.
    gem 'sdoc', '~> 0.4.0', group: :doc

    # Use ActiveModel has_secure_password
    # gem 'bcrypt', '~> 3.1.7'

    # Use Unicorn as the app server
    # gem 'unicorn'

    # Use Capistrano for deployment
    # gem 'capistrano-rails', group: :development

    group :development, :test do
      # Call 'byebug' anywhere in the code to stop execution and get a debugger console
      gem 'byebug'

      # Access an IRB console on exception pages or by using <%= console %> in views
      gem 'web-console', '~> 2.0'

      # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
      gem 'spring'
    end

routes.rb

    Rails.application.routes.draw do
      root 'home#index'

      get 'about/index'
      get 'home/index'
    end

remember

You can always (temporarily) remove stylesheets to help orient yourself