A Dime A Dozen

When something is "A Dime a Dozen," it's common and easy to get and therefore without extraordinary value.
Example: 
- Look what I found!
- Oh, that's nothing. Those bracelets are a dime a dozen.

TURN OVER A NEW LEAF

To turn over a new leaf means to make a change in one's life; to begin over or anew. The "leaf" is not one from a tree but one from a book, as if one's life was a book.

For example: In the New Year, he decided to turn over a new leaf and improve his life.

BE IN THE DARK

To be in the dark means that you don’t know what is really going on in a particular situation because you were uninformed.

They didn’t want him to know, so they kept him in the dark about the company going bankrupt.