do you already have
Nicol Bolas, the Ravager,
Nicol Bolas, Dragon-God and
Dragonlord Dromoka?
If yes it's okay, if not, I would reccomend to invest the money in the mana base in stead.
Some ideas:
Exotic Orchard,
Fellwar Stone,
Arcane Signet (expensive),
Joiner Adept,
Sylvan Caryatid,
Cultivate,
Rampant Growth.
Then you could do alot of slot optimizations in oder to increase the efficency of the deck.
As example,
Reclaiming Vines. The important question here is, do you really need the ablility to destroy lands? If not,
Nature's Claim or
Return to Nature would much better options here, because they are a) way cheaper and b) are instants in stead of sorceries. a good spot removal (one target) works at instant speed and has cmc of 2 or lower (maybe 3 for special stuff).
Another card that catches my eye was
Foul-Tongue Shriek. It's fine for token decks but do you think you get enough dragons on the field that the card is worth the slot? It would be interesting for 5 or more dragons. with 23 creatures in total, this is already a big amount. and if you compare the damage the dragons do then, to the life drain from
Foul-Tongue Shriek.. err no.
A situation where I would like to play the card is sending enough tokens for a kill to opponent A and play this card on opponent B then for a double kill.
Think about the core points of your deck. what is it supposed to do? If you're sure about this, go through your cards again and think about they fit into this.
If you got some budget left, like already said, improve the mana base, since this is the biggest weakspot for 5 color decks.