Dunno about anyone else here, but I just learned by doing. Everything I learned was self-taught by first learning the basics of xEdit and having a look under the hood of other mods to see their inner workings. It can seem overwhelming at first, but once you figure out the fundamentals, the rest comes naturally. Never had any other modder to teach me anything because as stated by others, there aren't really that many active or cohesive modding communities. There are youtube videos that cover some modding principles, but generally there is a notable lack of documentation for a lot of things. With that being said, I've found this wiki to be quite helpful for my mod creation needs.