Kinda like asking what you might expect to spend on golf or fly-fishing ! All depends on
how much you want to shoot, how often and where.
You could start off fly fishing with a $ 75 or $ 100 "combo/outfit" ... just to say you gave it a try ... but a dozen rods, reels, lines, waders, nets, vests, Patagonia jacket, pontoon float and/or drift boat later, not to mention excursions to both coasts, the great rivers of Southern Alberta, Montana, Idaho and maybe a few trips to the Gulf coast & Caribbean ... well, it can add up. I have a couple of rods alone that go ten times the cost of a basic cheapy combo.
The Beretta 391 you mention is as good a start as any. I'd look at the 391 Parallel Target ... the SL if you're 5'10" + ... the RL ( about 1 " less LOP ) if you're vertically challenged. Good start. Buy decent 1 oz. target loads, not cheapo promo rounds. A few lessons from a good shooter/coach, especially one that is savy on gun fit will be a blessing & a wise investment.
And by all means, give-up golf entirely !
