This is the best tool to start with. Google made this tool for advertisers. As a publisher, you can use this tool for free if you have a free Google ads account. This is the best keyword research tool I have ever used. Some of the features are-
- 100% free without limitation
- Country-Specific or, Worldwide search volume.
- Check Organically Ranked Keywords of Any Website. Just put the URL on the box and enter
- Check Paid SEO Difficulty For Free
- Organic Impression, Organic average position, and lot more filter option
I use this tool to find out long-tail keywords. A key phrase comprising 4 to 5 words can rank easily without link building(whatever the difficulty is).
Google keyword planner along with simple google search can give you the most effective idea about low competitive keywords.
Keyword Research Idea: Find a long-tail keyphrase(3 to 5 words) and then simply search on Google. The result will show you relevancy. Visit the top sites and ask yourself- Can I make more relevant and useful content? If yes, go for it.
Put the link of your competitor site on Google keyword planner and find out the keywords they ranked for. Search on Google and analyze the contents. Now, create better content if you think the competition is low. Inbound link analysis is necessary for SEO.
If the content is relevant today or, tomorrow it will rank well. You can use Google ads to reach your client. The paid SEO difficulty score is shown on this tool.