It seems like you could cast any of the spells with "Buyback", cycle your cards with your boss ability, then put the buyback spell back in your hand. If any of those seem useful to you it might be worth adding to have something you can just recast over and over. Shrieking Drake also.

Capsize is in the maybeboard, but it's very expensive to buyback and if a Mindmoil effect is out, we lose it as soon as we cast another spell. On the pro side we can cycle the cards without card disadvantage, which is true for all buyback cards. I don't like Mystic Speculation, it feels like a bad Preordain - 3 mana for scry 3 and draw a card in sorcery speed. Whispers of the Muse is essentially 6 mana draw two cards instant - which sounds bad, but the flexibility of having a mana sink to draw cards or having a 1 mana spell to trigger Mindmoil while going off, seems good. Shrieking Drake seems extremly good, essentially it allows to cycle through the deck without card disadvantage. The only thing I don't like about it, it's utterly useless without a Mindmoil effect.

Thank you very much for the input.

To protect from self mill you may want to add Obstinate Familiar

I had Obstinate Familiar in, but it's such a crappy card if you don't have a draw doubler out and it's removed so easily - people somehow find it funny, if you mill yourself involuntarily :D - that I took it out.

Missed the part where you had nicely explained why no Obstinate Familiar in the description. Also, what are your thoughts on Jace's Archivist or Enter the Infinite in this deck?

Jace's Archivist is an alright budget option, but I don't like, that he has to surive going around the table once. If someone is bothered by the Windfall effect, the archivist just get's killed.

Enter the Infinite would probably be quite a good finisher, although not as reliable in killing the whole table in one turn as Omniscience. If we only have one of the win conditions on the board, drawing some 60+ cards will often be not enough to kill 3 people (Psychosis Crawler would probably do the job though). Toghether with Mindmoil or the commander it would probably be easy to finish out the game - I would definitly put Everflowing Chalice in the deck as a 0 cmc Mindmoil trigger - but just stringing together some spells would often do the job as well. With Alhammarret's Archive or Thought Reflection it becomes unplayable though. Also 12 mana is quite a lot for this deck. I would prefere Omniscience, but I think Enter the Infinite could easily replace Mizzix's Mastery as a budget finisher. I will think about it some more and maybe change it, thanks a lot for the suggestion!

Also instead of Master the Way you could add Spiraling Embers due to the cheaper CM cost, unless you really want that card draw.

I think out of Spiraling Embers, Master the Way and Fateful Showdown the last is by far the best. It's 4 mana, it's instant speed and it synergizes very well with the draw theme.

I added Master the Way because it kinda fit the flavor and I would've liked to kill someone with it. I think compared to Spiraling Embers the cantrip is worth the one mana, since Arjun really likes to keep a full grip, but honestly there are stronger options all together. Thinking about it, I will probably replace it for something else. Off the top of my head I'd say Curse of the Swine seems like an improvement.

Couple more cards that may work due to having a larger hand size Foil or Misdirection.