Wanting a recommendation for a basic CRM

I'm looking for a very basic CRM to take care of the following.

A list of around 500 contacts in a Google Sheets file, to email them from different email templates on their wedding anniversary, such as one email for their 1st anniversary, another email for the 5th, a third one for the 10th, etc.

Also, to email some of the contacts on their birthdays.

There are no other requirements of the database. No CTA's or selling them anything. All of them are past clients.

Would the cheapest solution be a cheap/free CRM?

or to use some automation between Google Sheets & Gmail?

or between Google Sheets, GMail & Zapier?

or another option that might be better that I haven't even considered?