II would recommend 148 grain wadcutters to begin with. They're not a high velocity load, and were designed as a target load for punching holes in paper. Theyre short and stubby thus hard to work with speed loaders, but are pretty good for training a nee shooter in the basics. After mastering the fundamentals, you can move up to semiwadcutters, which are more versatile.
First I would put some time into dry firing that 686 until I could press the trigger on DA and drop the hammer w/o disturbing the front sight. Then go to the range and practice ball and dummy drills. That's where you load two side by side, skip a hole and load s third. Spin and close the cylinder and engage your target. When the hammer falls on an empty chamber, you can tell if you flinched or held a good sight picture. This shows that you are mastering the trigger. Then, without ejecting the three spent cases, load three more in the empty charge holes and continue. Repeat this drill till you finish the 50-round box.
Welcome to the club and enjoy your 686. You might also look for a professional instructor in your area, as internet instructions sometimes fall a little short. Right now,funding 38 ammo might be a little hard . Consider shipping on the net and ordering what you want in bulk. If not, either of the rounds you mentioned would work fir training ammo b