I'm not sure about using the .38 for the range while packing the .357...
It's generally good practice to practice with what you intend to use.
I will say that I have shot neither cartridge so I offer no specific advice for the .357 or the .38
You do what I did when I taught my bride to shoot. Start them out on .38 wadcutter, it's a very mild but accurate load and teaches sight picture and trigger control. Then you move up to .38 ball and later +P. By the time we were finished (over a 2 week period) she was keeping .357 in the black at 25 yds out of a S&W Model 28. She still prefers a wheel gun so we keep a S&W Model 640 in the bedside with +P's.