mtg collector booster boxes Marvel Super Heroes Traditional Foil of any rarity replaces a Common in 33% of boosters MTG Collector Booster Box Commander

Another card that works well with Goldspan Dragon is Show of Confidence, first because you can cast a lot of spells in the same turn due to the Dragon, and second because each instance of it targets the Dragon again, basically giving you infinite mana

Rieton 16 Pocket Card Binder for YuGiOh Cards, Fit 1088 Cards Large Ringless Side Loading Pockets Trading Card Album Compatible with Yu-Gi-Oh Cards

Thematically, some of them have abilities that play well with other cats, like lifegain and +1/+1 counters, while other legendary cats are off doing their own thing

Legality depends on the tournament format -- Curse of Fool's Wisdom can be legal in some formats and banned or restricted in others