Chances are you’re reading this because Magento 2’s installation instructions for their Sample Data packages using Composer (link) basically suck. There’s a long list of packages that need to be manually required and in their very vague examples they say that you should be using version “2.0.0” when requiring those composer packages. That just doesn’t work because all of them are currently released under version 100.0.0 (yes: WTF!).
Before diving more into the topic, I should mention there are other ways to install Sample Data that might be easier. Particularly using the Magento’s CLI tool. That didn’t work for me either at the time of this writing but its likely you’ll want to use that in the future anyway because it has the potential to be much more convenient.
The following Composer command worked for me on a MacBook Pro (El Capitan 10.11.1) with PHP 5.6 but its generic enough to work anywhere if you have set up Composer and directory permissions correctly. If any of the packages fail then its probably because they renamed it, removed it, etc.
Like with any other commands you might find online, try not to recklessly copy-paste it into your console: instead, try to understand what’s going on. And of course please understand that you’re executing this at your own risk: what worked for me might not work for you.
composer require magento/module-bundle-sample-data magento/module-catalog-rule-sample-data magento/module-catalog-sample-data magento/module-cms-sample-data magento/module-configurable-sample-data magento/module-customer-sample-data magento/module-downloadable-sample-data magento/module-grouped-product-sample-data magento/module-msrp-sample-data magento/module-offline-shipping-sample-data magento/module-product-links-sample-data magento/module-review-sample-data magento/module-sales-rule-sample-data magento/module-sales-sample-data magento/module-sample-data magento/module-swatches-sample-data magento/module-tax-sample-data magento/module-theme-sample-data magento/module-widget-sample-data magento/module-wishlist-sample-data magento/sample-data-media
Hope this saves you some time! Now go back to the official docs and continue with the Magento 2 installation.