In comparison to the installation process on Microsoft Windows or Apple Mac OS you have to deal with the fact, that there are a lot of different Linux-based operating systems. So there are also different ways to setup your environment for kdebindings.
First you should check before starting to install something if your Linux distribution has ruby and/or the bindings preinstalled.
Start a shell on your Linux system and type and try to get the version of your ruby installation. In the case of a working ruby installation you get something like this.
> ruby -v
ruby 1.8.7 (2008-08-11 patchlevel 72) [x86_64-linux]
Maybe the Qt/KDE bindings are installed, too. For a quick check, enter irb in a shell to start the interactive ruby-shell. Try to load the bindings.
You can load bindings for KDE4 (korundum4) or only Qt4 by a require. Later you won't need to load Qt4 first when using KDE4, because on requiring KDE4 everything needed is loaded automatically.
If you got it so far you seems to have a working environment.
If you haven't ruby installed, you have two different ways to get it.
I recommend the first way.