Semmering offers a good allround package, with some technical (but not steep) sections, and some jumps. Its also good to get better at jumping, because there's also some smaller jumps. But if you want to go to the alps you will need to go further west in austria, semmering isn't really in the alps yet.
Regarding schöckl, I wouldn't say it's as difficult as some people make it out to be, I started riding there soon after beginning to ride mtb. It's a great place to learn more about bike handling and line choice, but there's not much variety in the trails.
Be aware that Schöckl is unfortunately closed until may.
