Keyword research is vital.
How does Google know what your pages are about?
Google knows what to rank you for based on the keywords in your title and the text of the blog post. You need to do specific and thorough keyword research to rank in Google.
You can't make up the keywords and expect Google to know what your page is about.
There are both free and paid tools that you can use to come up with keywords.
You can also search Google and look at the titles of the pages that are ranking for your search queries for ideas.