SEO can get quite complicated so you will have to have a proper strategy before getting started with any project for that matter. If you think you can do any sort of SEO without having access to appropriate amounts of data relating to the various keywords and niches then you will never be able to succeed in your mission.
There are countless pieces of information that you will want access to before you can plan an appropriate strategy to rank your website on the various search engines. This is why you will find most marketers preferring going for an seo api subscription as opposed to investing in countless numbers of tools that may be available in the market all having to do something with an aspect of SEO that you may be working on.
Apart from putting you in a better position to save money off spending on unnecessary tools, an SEO API would also enable you to become a lot more productive at work as you will be able to get access to all sorts of SEO data from a single platform. The thing for you to concentrate on is to identify the right SEO API service provider that would provide you with access to all sorts of tools that you may have a need for.