It is not easy to make money blogging, but if you stick to it, you should be able to increase your income over time.
Write about things that you know. It is easier if you write about what you already know. You can write much faster and accurately on subjects in which you are well versed. Even if the subject is not a popular one, it is better than you trying to write about things that you know nothing about.
Do not spread yourself too thin. Don't try to have 100 blogs. Try just one good blog, keep at it every day. Make sure that each post is at least 100 words. Try to post 1-3 posts per day all on your niche subject. You do not want to spread your subject too wide either, try to keep it as focused as you can.