Early Fusion Monsters have very specific materials, while later ones are less restrictive to account for power creep from newer cards
Blue/Green Luffy (OP16-022) is the clearest story of month one
"First-Ever Pokemon Trading Card Game World Champion Titles Won by Dylan Austin, 14 of Ann Arbor, Michigan and Mindy Lambkee, 10 of Kent, Washington IndexArticles"
Most tokens don't have a mana cost (though see below), so a token that ends up in your hand can't be cast unless you find a way to cast it without paying its mana cost
This promotes a feedback loop of sorts, where any hand that can access Spring can access all 3 of your core Gem-Knight names, which float or are Summoned by effects when moved between the hand, field, and GY
It's a scary Abzan card that can be built as an attrition-style deck, or with flat-out Necrobloom combos in mind