Not trying to be a jerk or anything, but realistically to get anything done you're going to want to self-learn by trial. A lot.
Start by taking a look at the Civ gameplay assets folder. <Install Directory>/Base/Assets/Gameplay/Data/
There you will find many game functionality things like Civilizations, Leaders, etc.
Learn what they are and how they work by reading them (XML is a pretty readable language, most of it will be self explanatory). If you don't know what something is, try and figure it out by changing it (backup the file before you change it; you will need to restart the game after changing those files) and seeing what that does.
Ask on the forums once you're stumped. Once you get a little more comfortable with that take a look at the .modinfo guide in the tutorial section and try to make a change via a mod instead of editing the core files.
Good luck.
(Note: This is what we're all doing, which is why I suggest it. The more time you invest doing this, the more you will know).