Welcome to the modern world! Not to sound too harsh or anything, but I think you would need to be living in a cave to not realize by now that:
(a) Google (and Facebook and ...) really do know who you are and will freely use that knowledge to whatever advantage they see fit (for social-network based advertising in this example .. google "google mail mining" and starting pulling on threads ... many quite old by now).
(b) If you are using a Gmail account (or communicating with a provider that uses a Gmail account (spoiler alert: don't)) for hobbying, then you aren't just making it an easy data mining problem for Google to figure out what your "interests" are -- you are literally sending them an email telling them -- and they are free to do whatever they like with that information.
(c) You really shouldn't discuss anything via Gmail that you wouldn't want the whole world to know about. (That's really true for unencrypted email generally, but we can save that rant for another day.)
So, if you care even a little bit about security, then just say "No!" to using Gmail for hobbying in any way, shape, or form.
Same goes for Google voice, btw.
And if you are really paranoid, well, just stay the fuck away from any Google service for anything related to your hobby. ;>
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And just FYI ... simply using various "pseudonym" Google accounts that you've never explicitly linked together may help you feel secure, but it's a poor kind of "security through obscurity". You need to also use Tor, VPN or some other IP hiding/randomizing scheme to make sure that accounts aren't correlatable by network usage. (For example: I occasionally create throwaway Facebook accounts for testing and if I'm not careful about IP addresses used when these "users" are created and log in to Facebook, they will almost immediately get recommended to be "friends" since, well, they probably are. Facebook correlates these different users because they frequently use a common IP address and so they are probably family, friends or cohabitants