Lots of variables to consider. what calibre you considering. 45 cal bullet holes are a lot easier to spot than 22 or 25. Rifle/action types can enter the calculation. You going to use the rifle scope as your primary viewing tool or you going to use a spotting scope too? You planning on shooting offhand, bench, or both?
How hung up are you on the-old tyme-look? The old external adjust scopes, Lyman targetspots, Unertls etc are really cool looking, but they are also collectors items now and can cost a bunch. some of the newer ones like the Mitchells etc are seen but I can't even think of $$$$$ numbers that high
However you can use a modern internal adjust scope with a simple weaver mount and do just fine. IN that case most any decent varmint/target scope can get you started. I started a few years ago with a discontinued Tasco . Something like a 12-24 variable from one of the Sportsman's Warehouse/Cheaper Than Dirt -kind of mail order outfits on a browning M-78 45-70. (And frankly I have a better gun and scope now, but my scores are not all that much better---'course scope and rifle are not al the equation either) An issue or two back Dale McGee had an article in the ASSRAJournal about using and mounting modern adjustable scopes. Frankly just getting started, I'd go that route. At least to start with. You can always upgrade as you develop.
At most of the EtnaGreen shoots, used scopes show up on the trading table, usually at very reasonable prices.
now maybe some guys who really know what they are talking about will weigh in