Looks like 7 wins by a large margin, no reason to wait any longer. Well, on the bright side, this is a pretty unique setting... on the other hand I'm gonna be winging a lot of it, so we'll see how this goes!
Your apprenticeship complete, you have moved into your family's ancestral home, a large mansion overlooking the barren wasteland far below the Walker. Walkers are magical creatures, created by mages of ages long past in response to what ever it was that ravaged the surface of the planet, they are 4 legged creatures(3 would have to tilt the entire island drastically to move) with thick layers of stone and dirt piled onto their backs that slowly travel the land, deriving sustenance from some unknown means. Each is usually ruled by a single government, with different "countries" only interacting when the walkers move close enough together to easily travel between. But all of this is common knowledge and you have no idea why you are thinking about it at the moment. Anyway, the most valuable part of your estate is not within the mansion itself, but hidden within a cliff below. Here, in a cave system reachable only through a secret passage inside your chambers, is a large magical laboratory, set up by one of your ancestors generations ago. It's a bit lacking in resources, but apart from a few recent innovations it contains every tool a mage could possibly need for his work. It even contains a number of books detailing the basics of the many schools of magic. You set to work cleaning out one section of the lab, dusting off the unused tools and making sure they are ready for use. After all, these tools and manuscripts are devoted to your favorite branch of magical study.
And what school of magic is that?(second and third place will be the secondary specialties)
(Yes, I'm ignoring the "with an ordinary house on top" part. Why? Because, having a house on top of a mansion makes no sense, it's just part of the mansion.)