Every student needs a good basic routine
Playing the same set of exercises every day is a useful warm-up that helps you become a more consistent player. Even professional hornplayers use a standard set of exercises to help them get ready for a day of playing.
Most players use exercises that their teacher taught them, such as the Farkas Warm-ups found in "The Art of French Horn Playing" by Philip Farkas. You may want to try the set of exercises I learned from one of my teachers, William Adam. They are linked here and can be downloaded as PDFs.
Good luck and good practicing!