Two main thoughts!
1) You can write about various topics but it's good to have a few interrelated hubs. Then you can link to yourself, become associated with a topic and get more followers.
2) If you're aiming for sustainable traffic and ad clicks, then it's generally best to write "evergreen" content - stuff that will be just as relevant in June as it is today.
For example, yesterday I really wanted to write about meaningful ways to celebrate MLK -- but I realized that any traffic I got through that hub would quickly taper off. I still plan to write about that topic somehow, but in a way that has more year-round appeal. (If I were rolling in cash, then this wouldn't be a concern.)
So, I wrote about crazy vegetables instead & gave some great recipes. Those are useful year-round.