If you want just to get pages' content, the simpliest way is to use open-uri
functions. They don't require additional gems. You just have to require 'open-uri'
and... http://ruby-doc.org/stdlib-2.2.2/libdoc/open-uri/rdoc/OpenURI.html
To parse content you can use Nokogiri or other gems, which also can have, for example, useful XPATH-technology. You can find other parsing libraries just here on SO.