Ok, as promised I arrived home and I'm going to help you out, I'll redo the suggestions I did on reddit and complete with the rest.

I would add Liliana of the Dark Realms to tutor some swamps, altho you already have several things to fetch lands, so it is up to you if you feel the need for it. Hatred is a card I recommend 100%, it's great as a finisher, and if your commander already has lifelink even better. If you can afford a Urborg, Tomb of Yawgmoth then Nightmare Lash and Lashwrithe are good additions aswell. Weathered Wayfarer, Herald of Leshrac, Leonin Shikari, Oreskos Explorer, Taj-Nar Swordsmith, Divine Reckoning, Bloodforged Battle-Axe, Grappling Hook and/or Fireshrieker, Felidar Umbra, Hammer of Nazahn, Infiltration Lens, Kusari-Gama, Thaumatic Compass  ^Flip, Myriad Landscape, Shizo, Death's Storehouse, Phyrexian Arena, Vona's Hunger, Crucible of Worlds. Torment of Hailfire and Exsanguinate are always good finishers in a black deck, and since you will be tutoring lands a lot you can guarantee a good value for X.

Also if your playgroup plays a lot with graveyard consider Bojuka Bog.

I think with the colors you have and playing Voltron you should add some pillowfort stuff to the deck, like: Ghostly Prison, Propaganda, Collective Restraint, Teysa, Envoy of Ghosts, No Mercy, Dread, Baird, Steward of Argive, Windborn Muse, Michiko Konda, Truth Seeker, maybe Darien, King of Kjeldor could work too.

From what you already have on the deck I would remove the following cards: Darksteel Ingot and Fellwar Stone are not necesary, I know both of these are fixing but you already have several lands with 2 colors and plenty of land fetching, you don't need these. Helm of the Host is great, I love this equipment but in this specific deck I am not sure if it is worth it. At least not for the commander imo, but to use it on the other creatures you have that offer utility, specially the ones with ETB or the "propaganda" creatures, then it is definitly worth to keep in the deck. Lightning Greaves is loved by so many people but I don't really like it much, I mean the 0 equip is great, plus the haste but I don't like shroud, yes it protects your crature but also screws you, while it is equipped you can't equip other stuff on the same creature or enchant it, etc... So if you have no other creature to swap it and allow you to target your commander again you are basicly screwed, I don't think it is worth to occupy a slot with it. Same goes for Whispersilk Cloak, blue already gives you unblockable if you want, not worth to have this with the downside of shroud, I'd rather replace it with Aqueous Form for example. Mask of Avacyn is nice to protect your commander but that's all it gives, if you need a slot for something this is a card I would remove. Vedalken Orrery... You don't need this, I know the ability is nice and quite tempting but in a voltron deck you don't really need this, I would only keep it if there was a free slot with nothing better to put in it, but even then I think I'd rather add some equipment or aura instead of this. Baleful Strix is nice but for 1 more mana I'd rather have Phyrexian Arena in play, much better. Dreamscape Artist is nice if you can play lands from the graveyard, with Crucible of Worlds and similar cards, which btw is a nice recommendation for the deck, Crucible of Worlds would help you get your lands back when facing land destroyers or milling decks. Also not sure about Emeria Shepherd, I mean you can deffinitly trigger her several times, but idk. I would test the deck with her and see how she does, if she doesn't seem to be useful most of the times I would replace her, for example for the same CMC I would prefer Herald of Leshrac, much more synergy with your commander. Jhoira's Familiar is nice too, but again it is also one I would remove IF a slot is needed for something else. I'm also not sure about Walking Atlas, I think most of the times it will be a dead card on the board because you won't have land cards in hand at some point, making him generally a wasted spot on the deck. Yes he can be great in some situations, but when putting cards in a deck you gotta try and put the cards that will be good in any stage of the game, not only sometimes, and this guy is one of those "sometimes" cards. I also think you don't need Disallow and Stoic Rebuttal. I mean as someone who likes to play blue, I know how good and safe it feels to have some counterspells but in this specific deck you don't need that many, I would even say none but since you are playing blue anyway, 1 or 2 could be helpful but no more than that, remember the goal of the deck is commander damage, you already have a lot of protection for your commander in equipments and/or auras, you don't really need counterspells to protect him, so if you need slots for other cards I would even say remove all counterspells. I'm not a fan of Detention Sphere in commander, yes if your opponents have the same card in play it is great, but most of the times it won't happen, again it is one of those cards that are good sometimes but not always so I'd take it out. Regarding your lands I don't like much of Submerged Boneyard and Forsaken Sanctuary, Sunken Hollow and Caves of Koilos would be 2 good replacements that are not very expensive. I would also remove Temple of the False God and put instead some basic land, I mean yeah that 1 extra mana is nice and can help you but I'd rather have 1 more basic land to fetch with the artifacts, etc.

To sum it up, I think this deck works best as a mainly W/B deck with a splash of blue, for some of the Propaganda effects it provides plus the evasion and card draw/selection. Other than that what you want for Voltron and to fetch lands you will find it on white, black and colorless.

One small note, I think you have way too many things to fetch basic lands, maybe you could cut down 1 or 2, not sure. That's one of those things that require some playtesting, never played with so many so I am not sure how good or bad it can be.

That's all I guess. I bet there are some more good things for this deck but I don't know it all, yet! I know some of my suggestions are not budget but you can just add them to the aquireboard section, for one day later if you decided to include them.

Helping you out with this deck hyped me to try and make one with Korlash, Heir to Blackblade, as a nod to your own deck. If you ever need anything don't hesitate to contact me here or on reddit.

Hope my suggestions were helpful, and kick your friends's asses with Dakkon. Stay well :)

Wintermoon

Wow I cannot thank you enough for this. I am very interested in your take of W/B main + splash of U, because I always thought of Esper as W/U first with a dab of B (mainly because of so many instant options that U offers). I appreciate your land suggestions as that was one area where I had no idea.

Thank you again!

I could suggest better lands, but are more expensive. Regarding the W/B vs W/U thing, in this specific case I think W/B is the better approach, because you are going for a Voltron deck. Out of the 3 colors your commander has White is the best for it, followed by Black and then Blue. Blue only offers some evasion and that's it. So, since you are doing a Voltron, Blue should be the splash color, imo. But that is the way I would do it, doesn't mean you have to do it that way, if it doesn't fit your playstyle or you don't like it. As I said, the way I see it blue here can be used for the pillowfort stuff, card draw/selection if you feel like you need it and that's it. Thassa, God of the Sea is another card I am not sure if should stay. Yes the scry is great, that is why I didn't mention her before, but in a Voltron deck I am not sure if she is really necessary. It's up to you. :)