A scene that they added that I really enjoyed was Percy burning the snacks he got from his mom. It shows how much Percy loved his mom and respected her to complete an activity usually reserved for the gods. One thing that he said that hit home is that he felt that he was finally making friends. I know he meant a certain someone in that statement which will make the betrayal more devastating.
One thing that I realized is that they are putting more emphasis on Luke in the series compared to the book. instead of Chiron or Annabeth explaining the ins and outs of camp, Luke and another camper are the ones that do.
During capture the flag, Percy is idle, waiting for something to do. I have seen online some inidividuals did not like this scene, but to me it was m favorite scene. I believe some of the older fanbase needs to remember that this show is for pre-teens. In the show they will act their age.