Ultimately, with close focus distance being equal, what makes the reproduction ratio get closer to 1:1? Is it how much/far it can telephoto?
No, it depends on the design of the lens.
So, I think I solved my original question and a diopter is not what I am looking for. What I want is something that extends the zoom range on my 17-55mm lens, and that something is a teleconverter. Now, I know what you guys are thinking that this is probably an even worse option than a diopter or extension tube. But, functionally, it's what I was looking for instead of a diopter.
No, a teleconverter won't help you. It doesn't mount on some lenses (usually mostly only mounts on super telephotos). They can be mounted on certain macro lenses to increase the reproduction ratio, but then working distance is greatly reduced.
The only thing you can get cheap is an extension tube or reversing ring. Both offer terrible quality. Photography is very much an expensive hobby, there is no cheap method that offers great results :/