I’d say it’s a combination, ubersuggest, keywords everywhere, ahrefs, semrush, search console, and Siteoscope. Each have a purpose.
Ubersuggest, and keywords everywhere is free. Keywords everywhere also plugs in nicely with Search Console when you’re looking at queries, will give you the extra data of rough CPC and search volume. In SERPs, keywords everywhere also has a nifty sidebar with variations of the original search string, and shows search volume in the SERP.
Ahrefs and SEMRush are great for an all-in-one solution. Ahrefs gives you better capabilities for ideation of long tail keywords, SEMRush gives you better capabilities for PPC data. Both have paid trial periods.
Siteoscope is great for rank tracking, and progressive rank visibility. It’s mobile friendly too (SEMRush and Ahrefs aren’t the easiest to manouver on a phone while in transit) – I use Siteoscope on the fly with clients. Free 30 day trial period.