Hi 
Welcome to the list! 
Our wiki is a tad confusing at the moment! Sorry about that. If you could help by suggesting improvements to make it easier for new people to understand how to get started then that would be a huge help. I think we lose potential volunteers but it's not easy to see how to improve it.
https://wiki.documentfoundation.org/Documentation/Development
Hopefully someone here will give you an ODFAuthors login so that you can straight onto reviewing or proof-reading a couple of chapters of the Guides themselves or even get into working on the content fairly quickly. The big push at the moment is to try to get the 4.0.x branch's Guides out as quickly as reasonably possible.
How-To videos seem to have suddenly become popular and if you have experience adding sound or writing a script so that short 2-3minute videos can be translated reasonably easily then that might be good.
If you have experience with xml then our in-built help has needed attention for many years although i think most reasonably sane people would avoid it for now, especially as a first thing to try. Working on the Guides is were you find most of the team-work and even kinda mentoring so that seems like the best place to start.
Good luck and welcome in!
Regards from
Tom 