Keep in mind that Black & White was when Trainer cards began being called Item cards, so if you utilize Junk Arm, you can grab Trainer cards from HeartGold & SoulSilver (Rare Candy, Pokmon Communication, Pokmon Reversal) or Items from Black & White
HR - Hyper Rare - Haiprea Hyper Rare cards, SR or RRR cards with a rainbow colour and different texturing
Use tools like the Mana Base Calculator to ensure your new sideboard cards don't throw your mana ratios completely out of whack, and the Hypergeometric Calculator can help you understand the odds of drawing those key sideboard pieces when you need them most
I definitely see this as the launching pad of a series of the other nine color combinations as well
Merfolk Branchwalker was a mainstay of the deck for a long time, but some stronger stuff got printed and I haven't been back for a while
This ultimately means there will be more cards in circulation and therefore, those that are out there will be less valuable