Collaboration promos (Pokmon x McDonald's, retail exclusives) have limited print windows, and many have no known print-run data publicly available
Since Pikachu ex is a Tera Pokmon, Noctowl [Stellar Crown] seems like a solid inclusion to search out all of the cool Trainer cards that you can include in this deck, like the aforementioned Crispin, or even finish games off with Briar [Stellar Crown]
Unlike previous sets, Gym Challenge introduced more complex card mechanics and a higher number of trainer-owned Pokmon, making it a favorite for those who appreciate the lore of the original video games
Last but not least, I think the best option for new players would be the Amber-Ruby Starter Deck A Seaworthy Crew released recently for Azurite Sea
White makes that part of the layer visible, black hides it, and gray makes that area partially visible depending on how light or dark the shade of gray is