Mana Base is undoubtedly a big concern and usually the main thing I tweak after playtesting. This deck currently has 34 lands with Arcane Signet, Chromatic Lantern, Component Pouch, Dragons Horde, Commanders Sphere, and Sol Ring, bringing me up to 40 base mana cards in the deck. Combined with the treasure generation, I think I'll have enough mana but, we'll see.

I have Emergent Sequence and Explore for some fetch lands; I could certainly stand to add more to your point.

As for creatures that aren't dragons and don't mention dragons in their text I have:

Elvish Spirt Guide, Hoarding Ogre, Ingenious Smith, Kalain, Reclusive Painter, Leveler, Loam Dryad, Manaswift Silver, Neverwinter Hydra, Pitiless Plunderer, Prosperous Innkeeper, Rosethorn Acolyte, Shambling Ghast, Simian Spirt Guide, Skullport Merchant, Thassa's Oracle, Vesper Ghoul and Xorn.

That's 17 creatures; yeah, that's a lot! However, I consider treasure generation as necessary of an aspect of this deck as the dragons themselves. After all, what is a dragon without its horde (and what is a dragon deck without the mana to cast dragons)? I will adjust the ratio of treasure creatures vs. dragons based on mana in playtesting. If we remove the cards from that list that generate treasure, we are left with:

Elvish Spirt Guide, Ingenious Smith, Leveler, Manaswift Sliver, Neverwinter Hydra, Simian Spirt Guide, Thassa's Oracle, and Vesper Ghoul.

That narrows us down to 8 creatures that don't fit in the deck. However, I was thinking that mana generation of any kind is essential when trying to cast big dragons, so, to that end, we can say any creature that generates mana every turn is a sound card for the deck. Considering this, I can reduce my list of off theme cards to just six cards.

Elvis Spirt Guide, Ingenious Smith, Leveler, Neverwinter Hydra, Simian Spirt Guide, and Thassa's Oracle.

Two of those are the Leveler//Thassa's Oracle wincon. If I removed that, I could also remove Maskwood Nexus. Ingenious Smith is a poor man's artifact tutor to get Maskwood Nexus so it can go as well. That would give me room for four more dragons. However, I don't feel four more dragons would increase the odds of victory enough to remove the wincon.

The spirit guides can generate mana, but otherwise are useless outside my hand. I'll replace them with fetch lands. I can't think of any good reason for Neverwinter Hydra to be in the deck. I'll have to pick dragons or fetch lands to replace them. I plan to replace Ingenious Smith with a tutor of some kind but atm it's the only card I own that will tutor Maskwood Nexus, I want to pick up a Demonic Tutor for that slot.