I also started my novel from the True Love competition on here after a friend showed it to me! I have a variety of story ideas in play already, but I wanted to do something new for the competition, and I knew I wanted it to be fantasy-based. Eventually, I decided I wanted to play around with the idea of blood knights, which led me to create Fia. Opposing him, I ended up with Eli as our resident world-traveling thief. And since I hadn't yet written a fantasy story that involved dragons, I decided I needed to work that into it as well.
This was a very fast-paced creation process, given the time frame of the competition and the fact that I wasn't starting right at the beginning of it. There was a lot of world-building along the way, but I eventually settled on the state of the world with the empire and what the conflict would be in various places throughout the world and story.
Part of this, because of the nature of the competition, settled around the romance between Fia and Eli, or what would eventually be their romance. That part became a bit of a play on the prince needing rescue, only our prince happens to be a knight who is also quite capable of killing a dragon on his own, so rather than the traditional fairy tale story of princess-knight-dragon, we've got a blood knight, thief, and empire!
The magic system and how the shadows actually worked took a little more time to play with. But I really love the idea of in-between places and other worlds, so this gave me a chance to introduce that concept into the story as well through the magic itself. Plus, lots of fun new creatures! I've always been a sucker for good bonds between characters and animal companions 
I also knew I really wanted a story where I could play on the whole idea of "all that glitters is not gold" with characters who aren't wholly good or bad, and ultimately how love kinda saves us from the worst of ourselves. And from that, I created Dance of Blood and Faith!