A basic start:
Download SQL Express 2012 SP1 with Advanced Tools. Install, and experiment with it.
A cheap start:
Buy SQL Developer edition, install and experiment.
An expensive start:
Become an MSDN subscriber and download whatever you need for development.
Download two or more different versions (one of which is the latest), and install both (one as a named instance) - now you can play with a more enterprise environment.
Find examples. Try to accomplish them in different ways. Compare the results.
P.S. Focus on backups and restores first - that way, you can have a good starting state, try something, fail, and then get back to your starting state for another try. I like Ola Hallengren's procedures, which I modify slightly. http://ola.hallengren.com/