I think you might be going about it the wrong way.
Most people do not write thier own Gcode. They use programs to do it for them.
These programs are called CAM programs.
You insert the drawing you have into a CAM program and it will automatically concert it into Gcode.
The only reason I introduced you to CNC simulator was because you were asking questions about how to write your own gcode by looking at a picture.
I recomend you download a program called Sheetcam www.sheetcam.com
This program is shareware and will make little gcode file for you without needing to buy it. It costs $150 if you did want to buy it.
Mach2 although it is primarily a program for driving your machine, it also can create basic gcode too. Again it is trial ware and cost 150 bucks.
I feel for you, and wish I could sit beside you for just 1 hour so as to make it all clear for you. When I entered into this all, I was exactly like you. So much to learn and tons of new terms etc. It was a painfull few months. You will get there.
I recommend you just start by making your machine even if you dont know how to use it. When I had finished my first machine I did not know how to use it either. But if you break the whole thing down into small "Chunks" you will get there. Promise.