Citing someone else's idea??? (but not published work)
I just want to cite their work and ideas properly as a majority of the basic content is not my own.


Given that the majority of the content is not yours, you may want to make the person a co-author (or co-editor, etc.). That would appropriately recognize the work the other individual has made in the work that you have adapted.

Alternatively, if you feel most of your work has been editorial rather than creative, you could state:


  by X (arr. by Y),


where X is your friend.