If you want something that’s approved for production use, then you should use Server 2012 R2 with all patches installed (including KB3000850). This includes the “DSC 1.5” changes which make it quite a bit easier to use, and forward-compatible with configurations authored / compiled on systems with PowerShell 5.0.
If you’re feeling frisky, you could still use Server 2012 R2, but install the latest version of the WMF 5.0 Preview instead. This is pre-production software and you may encounter bugs, but DSC functionality is much improved by new features such as support for class-based resources (much nicer authoring experience), better integration with third-party tools (Chef and Ansible can already take advantage of the new Invoke-DscResource command, and I think Puppet might be there as well), the ability to debug resources as they’re being executed by the LCM, and so on. WMF 5.0 will be officially released along with Windows 10, I think, some time this summer.