Can't go wrong with the Google Keyword tool, SEMRush and Google Trends. The Keyword tool for volume estimates, SEMRush to see what keywords competitors are ranking for/targeting, and Google Trends to make sure the traffic is actually coming from countries I'm trying to target. Gives a relatively accurate picture of when to expect traffic spikes and seasonality insight.
More on this How to Do Keyword Research with SEMrush Keyword Magic Tool Post Maria Raybould SEMrush Toolkit for SEO Ebook Mar 16, 2018 Intent research: Confirming your keyword intent assumptions with Google ads Webinar recorded on Sep 20, 2018 Of course, knowing where to start can be difficult. Below you'll find the five best SEO keyword research tools I recommend for startups to begin a well-rounded keyword foundation for your campaigns.
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.