You have an overwhelming amount of enters-tapped lands which I think will be troublesome and somewhat frustrating when you need the next land to produce mana right away. One of the best solutions to your 5-color problem in this deck, that I can think of right now, is Chromatic Lantern, because it not only removes any color issues you face (like that triple green Garruk) but also accellerates your mana to start playing your dragons earlier. Then you can replace your lands with others that can tap for mana right away or even some utilty lands that can normally only produce colorless mana.
Also, having your mana accel on rather fragile creatures can get you into trouble, especially against more removal heavy red and/or black decks. Since you are in green, mana accel based on land searching is abundant and more secure. Sakura-Tribe Elder can serve as a chump blocker as well as a Rampant Growth, for example. combined with Cultivate and/or Kodama's Reach you can get to 5+ mana really quick and have whatever color you need for whatever dragon you have in hand. That's how my own 5-color dragon deck operates and it does fine with only basics and about 10 budget duals of the Lantern-Lit Graveyard kind. Of course, it needs basics to fetch and the majority of the lands can produce green, because it needs green to start the fetching.
There are only 12 creatures with higher power/toughness in the deck, so Nissa's Revelation has a rather high chance of coming up short, even with its scry 5. A different draw spell, and a less expensive one (like Harmonize), would serve better in my opinion. Or include more big creatures. Things like Indrik Stomphowler or Wickerbough Elder even give you some means to battle artifacts and enchantments.
Lightning Bolt seems out of place here. Yes, it is the pinnacle of efficiency for red damage spells, but its purpose is to kill creatures, right? After all, you plan to kill your opponent with dragons. And if you want to kill creatures, and you are in black, it seems ridiculous not to include an actual creature killing spell in its stead, like Terminate (because you are also in red). If you want to be able to deal with planeswalkers, too, well, Hero's Downfall, Dreadbore, Never // Return and Ruinous Path can take care of those, and with more certainty.
I would also include a sweeper spell, to clear the board before you start bringing out dragons. My deck uses a playset of Slice and Dice for this, because most of my dragons can survive it, and sometimes cycling it is enough so I don't even lose a card. Of course, this makes using BoP and other small creatures for mana accel even less desirable. Things like Languish, Anger of the Gods, etc. should also work out well. The goal for these spells is to halt the opponent's creature development and battle overly aggressive decks. Most of the time, the first dragon I play is Ryusei, the Falling Star, because killing it also kills the board usually, and your first dragon in the game carries a big "kill me" sign while the opponent often has the means to do so at the ready. After all, it's the first thing you play that actually needs to be killed.
You may also want to tutor up a specific dragon. The costlier ones you can get with Fierce Empath, which is another small creature itself that can act as a chump blocker to buy time. Sarkhan's Triumph is another option. Of course, being in black allows you to use that color's abundant arsenal of tutors as well.
Land
4Haven of the Spirit Dragon
4Temple of Abandon
2Temple of Malice
2Temple of Plenty
1Temple of Mystery
1Jungle Shrine
1Crumbling Necropolis
2Gruul Guildgate
1Breeding Pool
1Thornwood Falls
2Jungle Hollow
1Dragonskull Summit
1Forest
1Mountain
Planeswalkers
1Garruk, Primal Hunter
4Sarkhan Unbroken
3Xenagos, the Reveler
Creatures
2Atarka, World Render
2Dragonlord Kolaghan
2Silumgar, the Drifting Death
2Dromoka, the Eternal
4Thunderbreak Regent
2Courser of Kruphix
4Sylvan Caryatid
3Birds of Paradise
Enchantments
3Palace Siege
3Trace of Abundance
Sorcerys
3Nissa's Revelation
Instants
3Lightning Bolt
I plan on getting more Duel/Tri lands to help the curve and switch things out as well.
Also, having your mana accel on rather fragile creatures can get you into trouble, especially against more removal heavy red and/or black decks. Since you are in green, mana accel based on land searching is abundant and more secure. Sakura-Tribe Elder can serve as a chump blocker as well as a Rampant Growth, for example. combined with Cultivate and/or Kodama's Reach you can get to 5+ mana really quick and have whatever color you need for whatever dragon you have in hand. That's how my own 5-color dragon deck operates and it does fine with only basics and about 10 budget duals of the Lantern-Lit Graveyard kind. Of course, it needs basics to fetch and the majority of the lands can produce green, because it needs green to start the fetching.
There are only 12 creatures with higher power/toughness in the deck, so Nissa's Revelation has a rather high chance of coming up short, even with its scry 5. A different draw spell, and a less expensive one (like Harmonize), would serve better in my opinion. Or include more big creatures. Things like Indrik Stomphowler or Wickerbough Elder even give you some means to battle artifacts and enchantments.
Lightning Bolt seems out of place here. Yes, it is the pinnacle of efficiency for red damage spells, but its purpose is to kill creatures, right? After all, you plan to kill your opponent with dragons. And if you want to kill creatures, and you are in black, it seems ridiculous not to include an actual creature killing spell in its stead, like Terminate (because you are also in red). If you want to be able to deal with planeswalkers, too, well, Hero's Downfall, Dreadbore, Never // Return and Ruinous Path can take care of those, and with more certainty.
I would also include a sweeper spell, to clear the board before you start bringing out dragons. My deck uses a playset of Slice and Dice for this, because most of my dragons can survive it, and sometimes cycling it is enough so I don't even lose a card. Of course, this makes using BoP and other small creatures for mana accel even less desirable. Things like Languish, Anger of the Gods, etc. should also work out well. The goal for these spells is to halt the opponent's creature development and battle overly aggressive decks. Most of the time, the first dragon I play is Ryusei, the Falling Star, because killing it also kills the board usually, and your first dragon in the game carries a big "kill me" sign while the opponent often has the means to do so at the ready. After all, it's the first thing you play that actually needs to be killed.
You may also want to tutor up a specific dragon. The costlier ones you can get with Fierce Empath, which is another small creature itself that can act as a chump blocker to buy time. Sarkhan's Triumph is another option. Of course, being in black allows you to use that color's abundant arsenal of tutors as well.
Former Rules Advisor
"Everything's better with pirates." - Lodge
(The Gamers: Dorkness Rising)
"Any sufficiently analyzed magic is indistinguishable from science."
(Girl Genius - Fairy Tale Theater Break - Cinderella, end of volume 8)