the beauty of blogs is they can really be about anything you want! some people use it more like a journal where they tell stories about their week, but others have more of a theme on their interests, or just their opinions on random topics or even a mix of all of the above, it’s whatever you’d like

I'm also new to making proper blogs. The most blogging I've done is on my Tumblr, which is far from professional. That said, I recommend looking at the blog categories. Maybe narrowing down what categories you're interested in will help you think of things to write about.