New player: Question about cards that are only from Master Packs and White Forest cards

When I tap a card, then tap how to obtain, about half of the cards in the two decks I want to make only come from Master Packs. I was told to avoid these as a new player (could be wrong)

Does that absolutely mean they only come from Master Packs? Or just currently only available from Master Packs? For example; are there any selection/structure/secret packs that maybe aren’t in the shop right now? Or would how to obtain show them too?

Thank you in advance: trying to get some White Forest cards.