Kae's greatest strength is the sheer quantity of cards that synergize with her passive and enable her to power up her stats for a cheap price. Theoretically, any card that lowers defense can be used as a weapon for Kae. I'm on Fire! and Rainbow-Colored Circle are must-have cards for Kae that will take 6 of her 10 card slots, as they are easy to use, provide massive power, and don't help the opponent nearly as much as high-level battle cards.
While it seems like a pretty big risk to bring, Big Magnum is a good backup card for I'm on Fire!, and the risks it brings don't mean much to Kae since even someone using I'm on Fire! against her will easily KO her, and if someone else uses it, they are now easier for Kae to KO
While somewhat more difficult to use, if she packs Poppo the Snatcher and is lucky enough to draw it, they will have a permanent attack boost that can be stacked with I'm on Fire!, etc, for even greater results.
Accelerating Sky will give Kae a +1 ATK boost, and since opponents will also get the -1 DEF debuff, Kae is much more likely to KO them. It also boosts everyone's EVD, which can be vital for Kae since she relies on EVD more than most characters. Since it isn't a battle card, Kae can use it to combo with her battle cards for devastating results. It can also combo with Blazing!, although its not as reliable as using a battle card.
Heat 300% can be really good for Kae as she is more likely to KO someone who landed on it, while she will gain a +2 ATK boost until she gets into a battle. Since its a norma 1 trap, it is also Kae's best answer to shutting down Arthur's hyper, Branch Expansion Strategy.
While often not the best choice, Kae has the advantage of being able to use Sink or Swim without losing any attack power, given that the -1 DEF compensates for the point of ATK lost. The player would likely want to use this after using Blazing! or one of the previously mentioned nonbattle card to ensure Kae is strong enough to KO the oppoennt.
Cloud of Seagulls and Indiscriminate Fire Support can be used to deny Kae a KO, whether it KO's her target, or herself. However, Kae can also use these cards to KO herself to get behind someone, or to weaken a target before she fights them.
Healing cards like Saki's Cookie, Pudding, Portable Pudding, and Dinner can bring players out of range for Kae to KO them, although they wont do much against Kae using her ATK boosts for any character with worse defenses than a tank.
Since Kae only gets 2 ATK when she initiates battle, the player should try to stay behind Kae and attack first if possible.