About Fair Use
Does your work incorporate existing work that you can obtain permission to use? (i.e., work created by someone you personally know?)
No, it doesn't.
Does your work incorporate existing work that is in the public domain?
Yes. The images that I used in the posts published on my website and my Instagram are images free of copyright downloaded from a website database.
Does your work incorporate existing copyrighted work that you do not have a license to use, such as a clip from a popular movie or song? Apply the fair use doctrine to your work, and evaluate the strength of your claim to fair use.
As I am using other authors' plots and characters as a reference, it may be argued that I am incorporating copyrighted materials. Otherwise, the law doesn't protect ideas, therefore it is possible to modify or incorporate concepts or ideas created by other writers without having legal issues. On the other hand, as I will create my own stories, even if I copy a particular concept or idea used by those authors that happened to be copyrighted, I will transform that idea to fit my creation.