I keep hitting portals like right in the middle of the path so they're kind of hard to avoid
I did that for a while now I got pretty good at it, I turn off the sound from 3DS and listen to something else to help consenteate.
Just try and hit as many rings from the start as you can and gab the occasional ones later on that you can while avoiding the bad purple balls.
If you get too slow try entering a double ring at least instead of a single ring to increase chances of a legendary