This is an amazingly dense selection. Both from narrative points and for meaningful reflection.
Saul again fails to kill someone and this time really upsets God. Plus we have three origin stories for David. One his is anointed by Samuel; two he is the musician who calms Saul's late onset madness; three he slays Goliath. (P.S. he will slay Goliath again.)
Of course, some of David's origin stories can be reconciled. Samuel could have anointed him and then he just happened to be the kid who plays the harp. Or maybe Samuel anoints him, everyone forgets that, and then he happens to show up at camp with his brothers, and no one says, "Actually, aren't you the anointed king of Israel? Maybe it does make sense for you to fight Goliath." But, the thing is the authors didn't do that. They gave us three sides of who David was.
It is interesting to think about these stories as what is required of the ideal leader.
On a theological note, when Saul is caught having allowed King Agag to live and some of the animals from the city, he tries to rationalize saying that he left the animals for a sacrifice. Samuel is having none of it, and in some crazy baller scene kills the king himself. Then we have this: "And the LORD regretted that he had made Saul king over Israel." 1 Sam. 15:35.
God, regretted. Interesting.
Translational note: the words translated in the NVI as siervos y cortesanos are both translated as servants in the NIV. 1 Sam. 16:18. Courtesan or courtier has a different connotation to me than servant.