You could focus only on cards that create black tokens, but that would leave a lot of great token generators out of this ranking: Treasures are colorless tokens, Bastion of Remembrance creates a white creature token, Pawn of Ulamog gives you a colorless Eldrazi token, etc
Red generally focuses on creature and artifact destruction, so having a card on hand that can deal with enchantments, planeswalkers and lands is pretty neat
Trafalgar Law ST10-010 Character Purple 4 Cost 5000 Power Slash +1000 Counter [Blocker] (After your opponent declares an attack, you may rest this card to make it the new target of the attack.) [On Play] DON
How did you get the assignment for designing the precons
Astrid Peth Ive highlighted a couple of cards already that play well with incidental artifact tokens, and Astrid Peth does that while also generating such tokens immediately and over time
10 Magic Golden Flower There are Glimmers that players will want to keep in play for extended periods of time, and while those cards may have some high Willpower, opponents will focus on them to banish them from play and eliminate their abilities