When planning your SEO campaign, find cost-effective keywords so it will be easy for you to outrank your main competitors. You shouldn't give up on ranking for very difficult keywords, but concentrating on low difficulty keywords, as long as they bring qualified traffic, will help your site move up in the SERPs and earn more revenue.
Determining keyword difficulty is very hard to assess, yet several SEO tools, such as SemRush, ubersuggests and Moz provide fairly accurate estimates. They look at search volume, the competition's backlinks, the quality of the backlinks from authority sites and domain authority. SEO professionals don't agree on whether domain authority actually exists, so keyword difficulty tools may not use it in their calculations.
SEO tools also look at the amount of relevant content on competitor's sites and the length of the content. Someone who wants to rank in one of the top spots in the SERPs for a specific keyword has to look at the top three sites to understand how much work he or she has to do. Unless you have unlimited resources, working on a highly difficult keyword can be a waste of time.
Concentrate on creating relevant content if you want to knock out one of the top three sites out of the SERPs. If your website is new, you will not knock popular, well-established sites out of the top three spots for difficult keywords; don't waste your time. Great content helps you earn backlinks so you'll have two of the most important ranking factors covered; content and backlinks.
If you are an experienced SEO professional, you can estimate keyword difficulty simply by putting the keyword in and reviewing the top three website's content to see how difficult it will be to create better content and more of it. Your client won't be happy if you waste their money trying to rank in the top three spots for a very difficult keyword, such as insurance, and fail after a year. For more information click here https://www.reddit.com/r/SEO/comments/bgg020/anyreliabletooltogaugekeywordsdifficulty/.