Although they are over twenty years old, they are not as rare as 2nd Edition Pokemon cards, and therefore they are less valuable
[58] "The Pokmon Demo Game Plastic Pack", "Base Set", along with the subsequent expansions "Jungle", "Fossil", "Base Set 2", "Team Rocket", "Gym Heroes", "Gym Challenge", make up the "First Generation Sets" published by the original English-edition publisher Wizards of the Coast
Tiana - Celebrating Princess The jury is still out on how useful Tiana will end up being in constructed, but in a starter deck format where top-decking is all but guarenteed, Tiana is a game-winner
The cut is almost surely some of the previously mentioned Sam Black resource conversion stuff, and the empty sideboard slots are likely best as Collective Brutality
I know it's not for everyone, but if you like powerful rares, there are some rad ones like Cool but Rude, The Ooze, and Splinter's Technique