Affiliate Marketing Secrets

I have a novel idea that I’m working on that has no particular niche yet.its just an interesting narrative at this point.when I was planning everything out I noticed that even though the relationships wasn’t the center focus of the plot it played a major part in the story and the developement of my charecter.I was thinking it wouldn’t be to hard to convert the story into a romance,especially since I’m kind of just practicing my writing exploring different styles to find my strengths and weaknesses.what I want to know is what are some of the do’s and donts of writing a romance and what are some tips you have.
Can you have a romance that’s about multiple successful and failed relationships or does it have to focus on one main love interest?please help with anything you can.thanks.