Most collectors end up buying again and again from a few sellers whose grading they trust. Following those sellers saves you checking back.
Step 1: Click the seller's name on any listing to open their profile.
Step 2: Use the Follow button.
Step 3: See everyone you follow under Buyer → Following.
What you get told about
You hear when a seller you follow has a new listing go live. The alert comes when the listing passes review and becomes visible, not when the seller starts drafting it. So everything you are told about is something you can actually buy.
Too many emails?
Turn off new-listing alerts in your notification settings. You stay following the seller and your Following list does not change. Only the alerts stop.
Will the seller know? Sellers can see how many followers they have. Following does not give you access to anything beyond their public listings.