For your QT, you should do at least 50% a day, but may have to do more depending on how much you are feeding. Testing is the only way to be sure.
As far as your display tank goes, it is progressing as it should. Hold off on water changes until you see nitrates (hopefully in a week or two). Since there are no frogs in your tank, you will need to "feed" the bacteria. I use Dr. Tim's ammonium chloride, but others just throw in a pinch of fish food and wait for it to break down. Personally, I am not a fan of the fish food method.
I consider my tanks cycled when it can convert 2ppm ammonia down to nitrates within a 12 hour period.