I like brew installing `emacs-mac`[0] which installs a port run by a developer in Japan. My favorite feature of it (among other amazing osx specific changes) is the sub-pixel scrolling support in emacs.

When you setup your `init.el` you can call `(package-install x)` and if the package is already installed it'll do nothing but just make sure it's there.

If you wanted the whole thing figured out ahead of time I recommend using Spacemacs[1]

[0]: https://github.com/railwaycat/homebrew-emacsmacport [1]: http://spacemacs.org