Self portraits is a great way to work your pre-visualization. Since you don't get to see while you're shooting, you have to trust your minds eye. It also is good modeling practice and keeping yourself aware of how you look.
By the ways, working with a manual focus lens is not as hard as you may think.
I actually bought a new big Sigma to replace the kit lens. I needed something with a constant f-stop and autofocus for journalism, but I still love the 50mm f/1.8 for stretching the creative muscles further.