Brainstorm Ponder Expressive Iteration Fevered Visions Jori En, Ruin Diver Rielle, the Everwise Firemind's Research Yusri, Fortune's Flame Jhoira, Weatherlight Captian Kraum, Ludevic's Opus Niv-Mizzet, the Firemind The Royal Scions Ral, Izzet Viceroy Squee's Revenge Aegar, the Freezing Flame Rhystic Study Counterspells with a hint of Redirection It's not blue without a counterspell or two
Since your theme is self-mill, I also really like The Master, Transcendent which is in your Sideboard
That last card is especially interesting as it is double-sided
34,99 One Piece
But such cards may be too expensive for updating the collection
I recommend you check out one of my favorite series, The Over/Under by Kyle Massa