I was re-watching season 2 episode 1 and the episode opens with both interesting scenes that are already telling about Luna and Ambar's characterizations. The first scene is Luna being comforted with love by her mom after having a bad dream while it followed by a scene of Ambar and Sharon where she's being told she needs to be the best this year and while it's not said, it clearly means that you need to be the best if you want my appreciation and approval. So unlike Luna's parents, Sharon's love for Luna is conditional. I also love how the two are also often at the center of a lot of dances/presentations. It's actually the two of them that truly begun by fascination with rivalry on TV, they are truly well written, despite being in a show that, god bless it, is not very that well written. Also can we appreciate how good of actresses Karol and Valentina are, some of the best in those type of teen telenovela imo. Again, I was rewatching season 2, when Ambar is showing the doll to Luna and she's having a chilling feeling about it, Karol really acted the part. And same with Valentina in the entire season, some scenes she had with the mirror were genuinely creepy and intense. 

 The show also don't really tell us that Luna is a better singer/skater than Ambar (she fails a lot more than Ambar). Ambar can also be admired and is equally talented (I feel like Violetta for example loved to put on emphasis that Violetta was more talented than Ludmila while she was very new to this world unlike Ludmila who worked all her life to hone those skills) 

I love the many contrasts the writers decide to have between Ambar and Luna