I have heard that I need to buy XCode for a Mac to enable it to download the full gesture support on my iPad2, like the four finger gesture.
Can this be done without a Mac?
You can find the free Xcode tools on the Installation DVD of your Mac within the Optional Installs folder.
If you are running Mac OS X 10.7 you can get the latest Xcode 4 tools free on the Mac App Store.
As for enabling without a Mac it is not possible. These are developer features and anything developer related is Mac OS X only.
No. XCode is for Mac.