Okay, you've finished your book. Now what? The worst thing you can do is to continue working on it. Don't second guess yourself. I've said it before and I'll say it again. Find someone (not related) to critique your novel. Get an honest opinion, even if it hurts. If a reader who knows nothing about your characters and plot and gets lost or confused, possibly your novel needs more work.
If it's okay, stay in your genre and start another book. Editors don't want a "one book wonder." They want someone with several story ideas in the pipeline. What they want is one book a year so no matter how long it takes to get published, keep writing. That way you'll have several books in YOUR pipeline.
Another thing...DO NOT put your work on social media networks. NEVER! NEVER! NEVER! give it away. Why would a publisher want to give you a contract to SELL your book if you've already given it away for free? They won't.
Yes, I remember the story of how Diana Gabaldon got her shot at publication back in 2001. That was a decade ago in the infancy of the Internet when she posted her novel "The Outlander."
The old rules no longer apply.