The Rugers are good guns for the money. There are basically two styles of single actions in Ruger the Bisley griped Varquero and the normal grip Blackhawks. The Varquero's have no rear sights that can be adjusted so that is an issue. The new Varquero's are a lot smaller than the old style so not as tough. The Bisely grips are a superior grip for most people but adding a rubber grip to the Blackhawk solves the issue.
The .45 Colt (or called Long Colt) is a great round, maybe the oldest still going cartridge out there. It isn't dying anytime soon. This round is used in cowboy action shooting and can be downloaded or uploaded as required. If you wanted you could upload the round to .44 Mag power with out much trouble in a Blackhawk gun. One other thing is you can buy a Ruger Blackhawk convertible gun that shoots .45 ACP and .45 Colt this is kind of cool.
The .38 Special/.357 Mag has a lot going for it as well. The .38 Special is basically the same power as a 9mm round and cheaper to shoot than the .357. When you want a little more fun the .357 Mag is much more powerful. To get more power than a .357 Mag you need to go above a .40S&W I think. It might be close but the .357 has a lot of balls. The same projectile could be used in both rounds but I use jacketed bullets in .357 Mag and lead in .38 Special due to higher velocities. Another option with the Ruger is a convertible that gives you 9mm/.38S/.357Mag in the same gun. A fun set of choices. The Rugers are not a true copy of the Colt SAA for good reason. To be safe you should only load 5 rounds in a true SAA due to the hammer being able to fire off a round by accident. The Rugers designed this issue out of their guns years ago.
You would enjoy both of these calibers but for a first choice the .38S/.357Mag would be better I think. A lot more kick bigger bang from a .45 Colt. Try to get a friend to sit with you for a few reloading sessions to help you through the learning process. There a few things that can go wrong and an experienced person can set you straight.