That is a bit ambitious for producing a software at all (even if you have already previous knowledge). Is this an ultimatum? What is the context?
You can use any plain text editor (but not an Office Word processor) or a full-blown integrated development environment (IDE). The latter are usually too powerful and confusing for beginners and take long to load projects and long to learn. Best is to choose a more light-weight advanced editor which supports you to avoid mistakes (code highlighting, syntax checking). There are by the way more than just the ones starting with “VS”.
Examples for advanced editors:
Integrated Development Environments:
If you are really just a beginner with development in SketchUp, you should rather get some first experience right in SketchUp and explore interactively the Ruby API until you get familiar enough before you are able to write complete files of source code in an external app:
These propose you available Ruby methods and documentation, and you can immediately see the results and inspect them.