doctorhydrogen

Mishra's Bauble/Urza's Bauble- Especially since you're running both Viridian Longbow and Thornbite Staff (which combo great with both together on Glissa letting you kill every single creature in a turn). I've had a single Bauble draw me 10+ in a game more times than I can count. They're literally the two most potent cards in my Glissa deck, no exaggeration.

I prefer Do or Die to Diabolic Edict, because pretty often you can take out multiple creatures with it.

Go for the Throat- I personally try to avoid "destroy" effects when it's reasonable to do so. However my meta is filled with indestructible stuff like Theros gods, players using Tajic and Sapling of Kolfenor for commanders, etc. Plus destroy effects just let people play the card again from their graveyard, and in EDH a graveyard is often times a second hand. Sever the Bloodline exiles, so it deals with indestructible stuff, it gets the creature out of range of graveyard schenannigans, and it prevents enter-the-graveyard stuff from triggering like a Wurmcoil Engine split or Grave Pact sacrifice trigger. It does cost four mana and is sorcery speed, though, but it has flashback and can be used to also eat a whole pile of tokens with the same name, which is nice. If you need the instant speed, Silence the Believers exiles, too, but again, it costs four. I think it's worth it in my meta, but YMMV.

Naturalize- Same as above, I avoid "destroy" effects here, too. Naturalize won't handle a Theros god, a Darksteel Forge, etc. and it lets the card be replayed. I'd much prefer to use Fade into Antiquity at sorcery speed, or at least tuck the card with Deglamer or Unravel the Aether.

With that many creatures, Luring Predators could easily pop you 2-3 creatures per round in a four player game.

Quite a few low cost goblins there that would be really cheap to tutor up with a Citanul Flute

Nykthos, Shrine to Nyx. All those red mana symbols . . .

Could always run Snow-Covered Mountains so nobody else gets to leech off your Extraplanar Lens.

Nykthos, Shrine to Nyx would love all those black mana symbols.

Urza's Bauble gives you another absurd draw engine with Glissa in play.

Triangle of War functions similarly to Executioner's Capsule as recurrable removable, especially with that many deathtouch creatures.

Black Market is an absolute BOMB in Glissa. I had twelve counters on one in my Glissa deck just last night, and that was in a dual. I've had 20+ on it multiple times in four player games.

Ratchet Bomb is a must-have, IMO. A two-mana reusable token wipe is sick. If your meta doesn't have many token decks I guess it wouldn't do much, but I see so many that it winds up ruining someone's day every single game.

I personally would run Sever the Bloodline over Sudden Death and probably over Hero's Downfall. Yeah it's one more mana, but it will deal with indestructible Theros gods, it ends graveyard shenanigans, it has flashback, and you can sometimes hit multiple creatures with it if someone has tokens or is cloning, etc.

manabasecrafter.com is a great source for finding all available mana sources for your particular commander. There always winds up being one or two old ones I forgot about.

With that many instants/sorceries wouldn't stuff like Charmbreaker Devils, Guttersnipe, Talrand, Young Pyromancer, etc be better than the Goliaths?

Darksteel Ingot & Coalition Relic are both strictly better than Manalith. I'd probably run all any of the three Signets (Orzhov, Rakdos, Boros) over it, too.

Dreadbore is quite a bit better than Doomblade, but if cost is an issue then I'd still probably run Terminate, Mortify or Unmake first.

That's a lot of white mana symbols that would love Nykthos, Shrine to Nyx.

Mono-white plays really nicely with Crackdown and Mass Calcify.

Card draw is always hard in mono-white. Mind's Eye maybe?

You have Thran Dynamo in twice.

All those white mana symbols would probably like Nykthos, Shrine to Nyx.

Both Crackdown and Mass Calcify are really useful in mono-white.

I'd run Dreadbore and Unmake over Murde/Doomblade/Terror. Maybe even Sever the Bloodline, too. Personally if an exile effect is available for even close to the same cost I run it because exile will hit Theros Gods, Darksteel junk, Avacyn, etc.

Consider Dolmen Gate, too. It lets you attack recklessly with Kaalia to put a creature into play even in situations she's normally die, lets your dragons with cool on-attack abilities attack recklessly, etc.

Self-targeted Traumatize w/ Bruna makes friends cry.

Especially in a three color deck Chromatic Lantern is going to be a much better card than Obelisk or Borderpost. I'd replace one with Chromatic Lantern and the other with Orzhov Signet if you want that many mana rocks. In three color Felwar Stone tends to be solid, too, as does Exotic Orchard for a land.

Terminate and Dreadbore (or even Murder) seem superior to Doom Blade.

Aurification is a rather great pillowfort card.

Glad to see Fight or Flight in here as it's often overlooked.

None of those red cards would be legal with a mono-blue commander

Skyshroud Claim costs the same to cast as Ranger's Path but the lands don't come into play tapped.

I'd run Plasm Capture over something like Cancel. Yeah, it's one more mana to cast, but since you draw so many cards with Edric (and therefore have so many to play) having an extra 4-5 mana on your next turn essentially means that the one extra mana you cast for Plasm Capture puts one or two extra cards into play you would otherwise have been unable to cast. It's not Mana Drain, but it still makes my friends give me the middle finger on a weekly basis.

Wash Out isn't as good as Cyclonic Rift, but it's an invaluable card for me and I wouldn't run without it.

Skullclamp is a stupidly good card in lot of decks, but Edric might be the only one where it isn't given how much evasion you're running. Mask of Memory will probably draw you 2x as many cards without requiring any sacrifice.

I'd include one or two ways to deal with artifacts/enchantments that get past your counters. Beast Within at least, maybe a Deglamer/Fade into Antiquity/Unravel the Aether.

Reliquary Tower would probably be useful, you're not running too many color-intensive cards and you'll be drawing enough to take advantage of it.

Deck looks good though, and Edric is hella-fun. Enjoy it!

Putrefy would work fine, too, cheap and also kills enchantments.

Hero's Downfall wouldn't fit the budget theme. If he wasn't running budget then yeah, Hero's Downfall and Dreadbore over all three. Oh, and I see Terminate is in fact sub-dollar, so that would be the best budget option.

All staying under a buck:

Skyshroud Claim costs the same as Armillary Sphere and lets you flop the lands directly into play. Granted they need to be forests and not just any land, but I still think I'd run it first.

I'd run Murder over Doom Blade and Ultimate Price. One more mana to have no restrictions on what you kill would be worth it.

Deck absolutely needs some way to hit enchantments (and artifacts besides Vandalblast). Fade into Antiquity, Deglamer and Unravel the Aether hit both, and they do it in a way that lets them handle Theros gods, Darksteel stuff, and in the case of the last two tuck annoying Enchantment or Artifact commanders like Sharuum or Purphoros.

Butcher of Malakir makes everyone else saccrifice a creature whenever you sacc one. It's Grave Pact on a body. Both Blood Artist and Falkenrath Noble will gain you a life and hit your opponent for one everytime you sacc a creature.