I have no interest in plowing through Amazon itself looking for bargains.
When you sign up, just choose your favorite genres and you will get a daily email with selections (except Fussy Librarian which is weekly); 90 percent of the offerings are free, 99 cents or $1.99. When I see something that interests me, I read the sample. If it sucks me in, I get it. Sometimes it's the first volume of a series, or a digital boxed set of several volumes of a series.
This is how I get my free books. I have found so many great authors and good series through these services.
I follow certain authors on Amazon and get emails when they have a new release or a book goes on sale.
The Prime Reading list is very long and has some excellent stuff. You can have up to 10 at a time, for an unlimited period of time. When I get these all read, I can pick some more. I have liked some of them so much that when they became available at a low price I picked them up. If you have a Prime membership, it is part of the package. Free
First week of the month, I get an invitation to pick a book from Amazon First Reads. If I get one, it is mine to keep. Free