Enhancing Documentation
Project Management
Fixing BugsI do however recommend you choose a project that you are interested in, something you can use yourself. You'll find your time more rewarding if you can "stick" with a project for longer than just "improving my skills".
As such a good starting point might be something in a non-tech space, but which is a hobby of yours. For example a bird-watcher might seek out bird-watching-software and see if thats a good fit.
I say non-tech only because those areas are the least served. Tech programs naturally get the lions share of techie contributers. (Although clearly not the lions share of good docs.)
A good starting place is the issues. You can also check our documentation and make PRs for improvements. And feel free to jump into discussions. We also give swag to our first-time contributors as a token of appreciation.
They just launched a bounty program recently.