Here is a high level overview for what you need to do to get most of an Android environment setup and maintained.
Prerequisites (for Homebrew at a minimum, lots of other tools need these too):
- XCode is installed (via the App Store)
- XCode command line tools are installed (
xcode-select --installwill prompt up a dialog)
ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"