As advantage of the Lee collet die is that it will create more than enough case tension to prevent bullet set back. Lee's factory crimp die would do the same thing and might be better though I can't explain why. You may not need an expander. If you want to spend a very few dollars, buy the Lee Universal Expander. It will create a small funnel type lip on case mouth and will not expand the case. This approach permits saving existing case tension.
50 years ago I shot .355 9mm out of .38 Spl cases and used various tricks to create neck tension. I used stupid charges of Unique, and today I'm thankful that I have all my fingers. Am I the only guy here who has blown up a handgun?