One-Winged Angel: Turns into a gigantic cyborg to open his duel with Yuma, Kite, and Shark
This green cantrip fills the graveyard and puts a body on board that ramps you into a 4-drop a turn early
If King of the Oathbreakers phases in at the same time as one or more other Spirits you control, King of the Oathbreakers's last ability will trigger for each of them
Give this infect or lifelink and enjoy
Master Duel, at least up front, is surprisingly generous: Between bonuses distributed to early players, completing Solo mode without replays, and the first chunk of leveling up, you'll very quickly hit the 10,000 gem inventory maximum
Except, yknow, that campaign is set before Link monsters were a thing, and the anime's duels followed the rules of its time