The primary difference between a simple sharpening stone and a sharpening "system" is the guide that ensures a proper angle.
Sharpening systems employ sharpening stones and incorporate a guide to ensure you are sharpening at the angle you want, rather than guessing at the angle as you do with a simple sharpening stone.
So, if you want to do it yourself, but haven't been trained in the proper use of a simple stone, get a sharpening system that takes the guesswork out of the process.
In a short period of time, the system will pay for itself.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan