Since you’re new, I’d recommend just using the old PC to start and get comfortable. Once you’re sure you want to invest some money, you can either build it buy yourself something more energy efficient if you’re super concerned about that.
As for the best OS, just any server OS will do. I run Rocky Linux which is a RHEL derivative, but you can also try TrueNas or anything else you want. Even Windows Server would work if you wanted to go that path.
There are many paths you can take, and which you go down depends heavily on personal preference and the desired use of your system.
Since you’re new, I’d recommend just using the old PC to start and get comfortable. Once you’re sure you want to invest some money, you can either build it buy yourself something more energy efficient if you’re super concerned about that.
As for the best OS, just any server OS will do. I run Rocky Linux which is a RHEL derivative, but you can also try TrueNas or anything else you want. Even Windows Server would work if you wanted to go that path.
There are many paths you can take, and which you go down depends heavily on personal preference and the desired use of your system.