The reading material most appropriate at any level is the one that will keep your attention. Some people will read easier material even if the story doesn’t interest them, because the process of reading and learning is motivating enough to keep them going. For others, it’s better to read something in a topic/genre they enjoy, even if it’s a lot more work. Only you can know what will work for you.
That said, it often helps to read with others, since you can ask for help with grammar, translation, etc. Plus, reading together can help you stay interested, even if the topic/genre isn’t something you’d normally enjoy. There are plenty of book clubs here on the forums if you’re interested.