What you will find here is help with what you currently are working on, Anyway to start of with, if you want a stable private server you have to compile it yourself, and i would certainly not recommend a vanilla server (1.12.1) as the core has alot of bug's.
I would recommend to start out with a 3.3.5 trinitycore server and learn how to set one up.
If you would run into any problems under the installation and the guides, then please let us know.
Also a reminder would be to use the search bar to look for threads which may have the same problem as you!
How to setup your 3.3.5 Server -
LINK
How to cmake -
LINK
How to install and setup boost -
LINK
How to set up a Mysql server -
LINK