Use this analogy to help you understand and apply the serve. Start with a correct, sound swing path. Don't overcomplicate yourself with other things yet. A sound serve swing path to me is like an officer's salute motion. Your hand with the palm facing down moves forward and down and to the side simultaneously.
Once you get the feel of how the racket "bites" the ball, start working on the body and feet, which are to assist the arm/hand's motion. If it helps, think of moving the body as a snapping or falling foward for momentum.