Here’s how to install homebrew on OS X Yosemite.
Remove and clean up any previous installations:
rm -rf /usr/local/Cellar /usr/local/.git && brew cleanup
Install a fresh copy of Homebrew:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
Detect any issues using Homebrew’s doctor command:
brew doctor
Clean up any issues from doctor.
Install your software.
Now you’ll be running with Ruby 2.x (default in Yosemite) as well as the latest Homebrew.