I do plan on coming back to Nin and creating a non-budget decklist to really see her full potential, however, I imagine that some people won't necessarily be able to afford a very pricey deck. So this is the people who are in between. I'm going to name some cards that are worth bringing into the deck if you have a bit more change in the wallet.
Force of WillFantastic counterpsell, will really help you out in the long run, and is a true essential staple in blue decks for competitive EDH.
Mana Drain Same as above. Just a all around great counterspell
Pact of Negation Same as above
Grim Monolith + Power Artifact: Both of these cards individually are fantastic cards to run in the deck. Power Artifact goes nicely with the Scepter+Dramatic Reversal + Sol Ring Combo since you don't need an extra artifact to go infinite. If both of these cards can be run in the deck, you just added another infinite mana combo in the deck. Grim Monolith taps for and needs to untap. By using power artifact, you reduce its untap cost by , therefore allowing you to tap for , and use to untap (I'm sorry if all these symbols cause confusion)
Staff of Domination is another option to dump all your mana into, with a the Dramatic Reversal + Scepter combo, since it constantly untaps it, allowing you to tap down everything your opponent controls, draw cards, gain life, etc.
Back to Basics is truly ridiculous in this deck. Due to this being a relatively budget deck, you run a ton of basics, it results in there being a minor downside on your behalf. Also considering the fact that the deck runs off of a lot of mana rocks. You can punish those who run multiple colors and fancy lands, just to give yourself a massive edge to get ahead.
Stranglehold is a nightmare. I used to run a Doomsday deck for a while, and currently, my main list is a Captain Sisay deck. This deck says "No" to all of that. I have no idea how big of an impact it has on a casual environment, really depends on who you are against, but in a competitive format, this is definitely a card worth picking up.
Volcanic Island + Scalding Tarn + Ancient Tomb + Other Fetches: One thing that can definitely help out the deck is throwing in some good ol' lands. Lands are the key to any deck, and having just to right mana base will help with your consistency and not leave you stranded. Right now the deck is running 24 basics (This ends up working out really well with Back to Basics, but I regress). Running stuff like Volcanic, Fetch lands (Scalding Tarn, Arid Mesa, Flooded Strand, Etc.) will help out a lot. Ancient Tomb is another land that is worth checking out. It gets you higher up on the curve, and considering this deck uses a lot of artifacts (and once you tune it to be competitive, the amount of artifacts goes upwards)
Mox Diamond + Mox Opal + Chrome Mox are investments, but they do work. All these cards can be used in essentially any commander deck, and just ramp up the pace of your deck. In this particular deck, considering the fact that you can tutor out artifacts, it becomes extremely good. Also worth noting that with Tezzeret the Seeker you can -x for 0 and search out any of these mox.
Dack Fayden just fits perfectly in a niche for this deck. He gives you the ability to draw, which this card would utilize quite heavily. He can steal artifacts, which honestly is just hilarious - but it's also worth noting that more and more decks are using Paradox Engine, so you can steal one of the combo pieces you need, or you can steal some manarocks and get yourself into infinite mana with scepter. Who can say no to 2 artifacts?
Academy Ruins allows you to keep bringing back artifacts, and in a format which has quite a lot of artifact hate, and in a deck that has a lot of draw, no second thoughts on this addition.
Tolaria West has transmute for 0 - Walking Ballista has 0. Good talk.
