Plot comes first. The plot is the archictecture of your novel. You wouldn't build a house without a plan. If I wrote without a plot, it would just be a pile of bricks. Characters are your servants. They must serve your plot.
I've been following Jesus for 35 years. He's guided me, comforted me, encouraged me, challenged me, befriended me, and been my constant companion since November 8, 1981.