The easy way to setup Mac OS X to do libGDX game dev is to utilize homebrew
Homebrew requires xcode.
Install Homebrew:
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
If you need to install git and clone the project, do that first:
brew install git
mkdir ~/code && cd ~/code
git clone git@github.com:bploeckelman/LudumDare40.git
cd LudumDare40
Install Build requirements:
brew install caskroom/cask/brew-cask
brew cask install java
If you don't have a java IDE installed, you can easily download one
(IntelliJ in this example) with brew cask:
brew cask install intellij-idea-ce
Eclipse and Netbeans are also available through brew cask.
./gradlew desktop:run
The game should build and run the desktop version.