Plot and character are twined together like a vine around a tree. You can't have one without the other. In stories plot is the guideline and characters are the actors. When an event happens characters react and this reaction brings change, There are stories that are more plot centered and others that are character centered. As the writer, you have to decide on the balance but forgetting or slighting one or the other can make the story fall flat.
So plot out your story and develop your characters. The events in the plot will cause your characters to react and for changes to happen.