|Read my article here!|
Writing about a subject that is familiar to you is the easiest thing in the world. So when applying to write for publications and websites, approach those that you actually read. This way, you wouldn't struggle so much. Writing wouldn't feel like work.
However, as your skill improves, don't be afraid to take on topics that are out of your realm of experience. In fact, doing this will expose you to new people, new places, new ideas. As a writer, you should never say no to anything that will open up your mind!