Which comes first, plot or characters is much discussed by authors. There are some who find characters looking for a story and by using these chracters wants and needs a story evolves. Other writers have a whole plot down and are looking for characters. At least that's what they say. My truth is that plot and characters go hand in hand. Sometimes a character will take a turn that throws the story off balance and sometimes a plot wants to force the characters into actions they don't want to perform.
I've read some books that acually bore me. They show the characters in many scenes, incidents where they perform actions but these stories have no goal. There's no roadmap showing where they are going and what they want to achieve. They become chracter studies but not books.
Then there are stories that are all plot and the characters mean nothing to the road to the end. The characters could by anyone and often change their natures as the writer needs them to become.
So as you sit to write your story remember to keep your characters consistent and to have a roadmap they will follow to reach the end. This will make a satisfying story.