You can also ask your friend to suggest a topic and get some information and write same in your blog. If your main intention is to earn money from blogging then regularly update your old topics whenever you get more information on old topics.
A new blogger it is good to write on trending topic with less competition and more searched queries on that topic. I also suggest you to make a group of 2 to 3 blogger and combine all your work in one blog instead of creating 3 different blog.
The topic should have some quality information which good tips and suggestions.