>>287454809
>Should I upgrade to the index for the visual improvements and better hands or should I pull more mileage out of my vive? 
I'd wait on the Index for a while. It's still hard to get and there are still QC issues with the controllers.
>is there a reasonable full body tracking kit?
Depends on what you think is reasonable. Kinect and PS Move are cheaper, but pretty janky. Vive trackers are kinda expensive for what you're getting, but they're still the only good option.