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There is no such thing as "game development software"
What language you need to know depend on the platform and what you prefer.
Big games are made using C++. Games on cell phones and the net are usually Java. Microsoft is trying to veer you off to C#.
Once you spend two or more years learning a language, then you can start on graphics.
For Java you can develop on Linux or Windows using Netbeans, or Eclipse.
C++ you can use Eclipse on Linux easy. Also on Windows, but you have to also install an open source C++ compiler for windows.
Visual Studio Express is available from Microsoft for free which you can use Visual Basic, C++, and C#.
Once you have the programming figured out, then you can move on to finding graphics libraries to draw your environment There are others, but it seems open GL is most common. Or you can use a gaming engine to draw the stuff for you easier. nVidia has their PhysX out, but only works with nVidia products.
Good luck