You can assess the interests of individual list members by monitoring which pages they land on, and where they go from there. The process is explained by this example from Airbnb. They use click behaviour to ascertain the destination preferences and travel styles of customers and base their follow-up emails on those preference profiles. It's intensely specific, but it gets results!
There are lots of ways to buy an email list, but none of them will actually benefit your campaign. Why? Since the owners of these email addresses didn't explicitly agree to receive content from you, there's no telling how interested they are -- or if they're even a fit for what you have to offer. A bought email list is also in violation of GDPR (we'll talk more about this in just a minute).
My next answer: - You see, - I could easily charge $100 or even $200 for a copy of this unique Self-Send-Solo System, - but why shoul I? My main income are made from other websites I own, not from this one here - this one here is more for fun and of course I make money from sales, (after all I am a business man)