I am seeking the Title and Author of a book I remember reading once
and would like to read again.

There is very little I remember about it except for the following:

-- A good portion of the book follows the main character growing up. 
I seem to remember that he was trained by multiple people, the one
that sticks in my mind is that he learns to play poker for a living.

-- The second thing I remember about it is that he meets a woman with
an Imaginary child, that he can also see.

The only piece of information I can give about the book itself, is
that it was published BEFORE 1992.

Here is a possible match for the book you are seeking:

Stone Junction by Jim Dodge - hardcover published in 1989.  Note ,in
the partial plot summary below, the reference to trainers and poker.

A short but remarkable life of Daniel Pearse and his extraordinary
education. Daniel's unwed mother, Annalee, raises him in a shack that
serves as the hideout for an ancient counterculture society, the
Alliance of Magicians and Outlaws (AMO). Annalee falls for AMO poet
Shamus Malloy, who causes her violent death. Young Daniel, in pursuit
of his mother's betrayer, joins AMO and discovers a faculty that
includes Wild Bill Weber on meditation and survival; rancher Mott
Stocker on sex and drugs; Willie the Click on safecracking; and Bad
Bobby Sloane on poker.

Thats it, post it as an answer and Ill pay.