When signing up for newsletters or retail websites, you can create a dedicated Gmail address that can be filtered to avoid inbox clutter.
For example, if my personal email is email@example.com, then I can use firstname.lastname@example.org for any online websites I create an account for. The same goes for email@example.com, firstname.lastname@example.org, and email@example.com.
From here I can filter these non-critical email notifications out of my inbox by applying a label to these new messages and automatically archiving them:
Appending your original username with a plus sign and additional characters allows for virtually unlimited addresses… all being delivered to your original Gmail account.