Google doesn't even factor into this. Go to your registrar of choice (namecheap, etc), buy a domain, and setup that domain to forward all emails to your email address.

So if you have abraxas@gmail.com and you just bought abraxas.me, in namecheap you can setup *@abraxas.me to go to your gmail account, and then sign up for sites using whatever@abraxas.me you want. There's no + or - involved, use any word you want. Signing up for lemmy.world? lemmyworld@abraxas.me will go right to your gmail (or whatever email you use)