I wanna know what is the best distrobution for my pi? I also want a cheap Australian setup under $125?
OpenELEC will be most simple XBMC distro working right out of the box.
You basically have three distributions to choose from, Xbian, Raspbmc or OpenELEC. They are all free so I'm not sure what the "$125" part of your question is referring too. As for "best", that really depends on what your opinion on best is, each of these has their pros and cons, if you could specify then I'd be glad to help you further.