Example as ball machine: https://www.youtube.com/watch?v=3njcoDqyo1k
Examples as a ball lift: https://www.youtube.com/watch?v=dET0RMmQSZs
I recommend building an octagon-shaped wheel.
The two most important parts to consider are the width and the radius.
A larger machine is more impressive than a smaller one, but has to run slower.
Choose some elements which can be used from any angle, such as the Flipper, a Ferris wheel, or an Arm drop.
Also, keep in mind that the machine will inconsistently rotate.