As a home user with a single modest workstation, what projects can I do to gain skills for an enterprise sysadmin environment?

I've been using Linux for over 10 years, but I hit a plateau in knowledge when I had learned how to basically do everything a home user needs. I'm 25 with no degree and I want to transition to an IT career within the next year or two. I have trouble coming up with projects where I will learn things that will transfer to an eventual sysadmin or similar job or otherwise advanced knowledge. I know one thing I need to start learning virtualization, but what do I virtualize? What kind of things can I work on at home that will take me deeper into Linux and networks? thanks in advance