To research easy rankable keywords is not practical if you are not using any paid tools.
You can do it using following steps:
- Find keywords, you can use Google Trends, Google Keyword Planner, keywordtool.io, or any other free keyword tool.
- After that, look the first page results of Google.
- Do on-page research for each of the page (1st – 10th)
- Keyword usage.
- Content length
- Do off-page research for each of the page
- Do it for other keywords.
You can see, it is not practical to do it without paid tools such as Ahrefs or SEMRush.
Using Ahrefs, you can examine keywords in bulk.
After that you can see the keywords
As you can see, you can see the volume search of keywords, then KD which is Keyword Difficulty, the more is more difficult. Ahrefs KD’s factors only using off-page (backlinks) assuming we can optimize the on-page SEO.
You can try to look about keyword research at How To Do Keyword Research + 20++ FAQ. I hope you get insights.