1995 pokemon pikachu card 8 If tails Vintage Original Pokémon Base Set

All play modes : If you're looking for even more challenge, toggle off "Arena Play Modes" at the top right of the home screen to unlock every play mode in MTG Arena

I mentioned adding Kraum, Ludevic's Opus as a partner specifically to get blue cards in the deck

Splash white reanimator cards and pick dual lands is also an option, especially if you got Piru, the Volatile since you want to be able to pay his upkeep cost

Hyper Aroma, lets you search for up to 3 Stage 1 Pokmon and put them in your hand, this can give consistency to Stage 2 decks such as Greninja ex and Gardevoir ex

Descent into Avernus does the same while taking the table down a peg and putting them in striking distance of your Twilight Prophet trigger