@Gorillajay I think you have a pretty solid starting point there.
Because you don't have the reserve list cards, I might swap in a couple of imitations. The draw 7s are pretty helpful.
Time Spiral is my go to grave hate spell. So I would consider something like
Time Reversal ,
Echo of Eons or
Day's Undoing for that purpose. There's also the fact that you can deck yourself with certain cards. Moving your graveyard back into your library is helpful sometimes. You could also try something like
Clear the Mind. Point being, this is actualy a crucial slot. You need grave hate and way to shuffle your yard. Time Spiral does both of these things and more in that it untaps lands and is essentially a free spell.
There are some good
Wheel of Fortune imitations as well:
Reforge the Soul Wheel of Misfortune Change of Fortune Imposing Grandeur are all cards to consider. The best thing about the draw 7s is that they can really screw with your opponents, however this isn't the case with some of the immitations. In the case of wheel and spiral, they are hyper efficient for what they are doing. With a draw doubler you will always come out on top. It's just an efficient way to refill your hand too. Bonus points if you cast them at instant speed with
Invoke Calamity. Feels awesome!
Intuition fills a pretty unique slot in that is can tutor for any type of card which is rare for blue. Typically I get my draw doublers with it. If one of the cards you tutor for is a recursion piece, you are guarenteed one or both of the other cards you tutor for. I would say another tutor in this slot that can get either enchantments or artifacts would be advisable.
Long-Term Plans works fine.
Fabricate or
Whir of Invention also work to get Archive. The draw doublers are super important to get into play and stay there. Other common targets for Intuition will be ramp, combo pieces, or board wipes.
Windfall is a bit of trap card. Generally this will be drawing your opponents too many cards. I'd go with something different. If you are playing against other control decks it can seriously backfire. Giving another control deck 20+cards isn't a good plan.
Temple of Epiphany I don't like. One time of it coming into play tapped when you need the mana will show you why it's such a cheap card. A basic land would probably be better. An any color land, or
Prismatic Vista would be something to save up for.
Pact of Negation started to feel too cumbersome for me. I found myself all too often actually having to pay the pact cost. Probably a different counterspell or interaction piece here would be advisable. Pact shines in cEDH where you never have to pay the pact cost. You are comboing out and that next turn never comes because the game is over.
Strike It Rich has been a bit underwhelming for me. Sure, it's 1 cmc ramp but I just question if it's doing enough to warrant a card slot. Id still reccomend playing with it and seeing how it goes for you.
Thought Vessel,
Fellwar Stone, and
Coalition Relic are all decent I guess but I find myself moving away from artifact ramp in this deck in favor of the treasure rituals. reason being that we can recur them from our graveyard and they trigger Niv. Thought vessel is especally suspect because it doesn't create colored mana.
If you find yourself in a faster meta, I think
Mana Crypt and
Jeweled Lotus would both be superior cards to run if you can acquire them. Mana crypt doesnt play well if games go long. The life loss isn't inconsequential. Lotus can really boost the deck, putting Niv into play as early as turn 2 or 3, but that's literally all the card does. It's a use once thing. Not being an instant or a sorcery means we can't recur it outside of underworld breach. Both of these cards are certainly worth mentioning and considering depending on your playgroup and your playstyle and your budget.
Mox Diamond would be here if it were affordable. I had a chance to get one for $40 about 12 years ago >.<
Your choice of win-con is probably the thing that is going to set your deck apart. You can try
Reiterate + ritual to make infinite mana and copy anything an infinite number of times. That's the win con I've settled on. It also translates to infinite draw if Niv is in play. Just keep that in mind. You should avoid decking yourself since his trigger is not a "may" ability. I would say that if you go this route I would favor recursion cards that don't exile. Stuff like
Shreds of Sanity Call to Mind Mystic Retrieval . You don't want
Reiterate getting exiled. This always needs to go back to your hand for the combo.
But there are A LOT of other options you might find more appealing depending on your playstle.
Aetherflux Reservoir is pretty classic. There is
Dramatic Reversal and
Isochron Scepter. There's my old favorite
Inner Fire and
Comet Storm.
You could go storm with
Grapeshot or the like.
Thousand-Year Storm is a pretty solid include then.
Or you can simply burn people out with your commander! More hand-cycling spells and tutors to grab your draw doublers would be a good idea in that case.
Fabricate and
Whir of Invention are both solid includes to get
Alhammarret's Archive. You can also try
Long-Term Plans which will also grab
Teferi's Ageless Insight .
You could also try the infinite combos:
Curiosity,
Tandem Lookout, and I forget the other one. I personally don't like them but they are there.
Omniscience and
Dream Halls go semi infinite with
Mindmoil .
Dream Halls is actually a pretty fun card and plays well in commander because it can create some interesting scenarios.