To find what people are actively searching for, use Ahrefs (or SEMRush).

Free Keyword Generator is great for researching insights into the search landscape. I recommend this too: Free SEO tools.

Google, X (Twitter), Meta (Facebook & Instagram) and even Bing is a contender for paid ads. Google Analytics or PostHog? Both are good, Google Analytics is free but the GUI is annoying whereas PostHog is beautiful but it costs. PostHog is much easier to install too.