Type specific requirements and maintenance issues aside, I would take the view that when considering what to teach somebody who is new to aircraft with retractable undercarriage, it would be helpful to give them as much practice as possible with retracting and extending undercarriage. Thinking back at the flying I have done over a number of years, I would say that the modal activity would be teaching a circuit pattern in an aircraft with retractable gear. My organisation always cycled the gear on each circuit.
.
(I had to look it up before I used a mathematical term, the mode or modal value of a data set is the most frequently occurring value. It's a measure of central tendency that tells you the most popular choice or most common characteristic of your sample.)