There are 30 in total, including secret rares and ultra rare cards
Additionally, trainer cards act as items, allowing you to heal your team or search your deck for specific cards, while energy cards are placed on your Pokmon to allow for more powerful attacks
In this deck, Lumra will represent an enormous amount of ramp from all the lands you've stuck in your graveyard, as well as triggering any other landfall payoffs you're running, like Skittering Swarm or Omnath, Locus of Rage
It mildly improves the card but is a very small part of why the card is good
The Legend of Roku is a pretty medium impulse draw enchantment in red, but when you flip it, it turns into Potential Man
This could theoretically lead to a steep Secret Lair tax