I finally got to a place with G/R Monsters that I like. Needs a little bit of tweaking, but it's almost there.

Card Choices

Creatures

Elvish Mystic - I don't think it really needs explaining. I'm not really sure if it should be 4 elves and 3 Rattleclaws, or vice versa, but I do know that turn 2 Rabblemaster and turn 3 Stormbreath are bonkers.

Heir of the Wilds - an almost guaranteed 2 damage per turn, as no one wants to block it. Also trades up to anything as a blocker, and has a nice ferocious trigger.

Rattleclaw Mystic - in an aggro shell, this gets in over Caryatid.

Fanatic of Xenagos - I went back and forth on how much I liked this card. I think I've decided that I like it. At worst, you get in for 4 damage, usually on turn 2. Or you get a 4/4 body that dodges Lightning Strike and Anger. Trample is extremely relevant right now too.

Ashcloud Phoenix - flyers are great in this standard, with the ground usually being clogged up. Resilient against removal as well. I'll honeslty probably remove this for Flamewake Phoenix after Fat Reforged comes out.

Polis Crusher - I'm not sure about this one. Trample is great, and protection from enchantments is relevant as well. We'll see how long this stays in.

Polukranos - I'm not a big fan, but he's a good body.

Stormbreath Dragon - hasty 4/4 that dodges white removal, and punishes the U/B and U/W Control decks of the format.

Instants and Sorceries

Lightning Strike - spot removal and reach.

Anger of the Gods - it takes out a fair number of our creatures, but the deck should have enough threats to get through it. Against decks like Jeskai and Mardu Tokens, Anger is basically a Time Walk.

Stoke the Flames - I think this is good enough, especially with Rabblemaster. 4 damage is relevant, and just flat out good I think.

Crater's Claws - spot removal and reach, but a bit more flexible.

Sideboard

Destructive Revelry - comes in with Back to Nature usually. Good for a bit of reach and blowing up problem Enchantment Creatures (looking at you Doomwake). Obviously good against U/W Voltron.

Back to Nature - enchantment hate package. Important against U/W Voltron, G/B Constellation and Whip decks.

Anger of the Gods - two more. They come in against more aggressive decks.

Barrage of Boulders - again, for more aggressive and "go wide" decks.

Fated Conflagration - I really think this card is underrated. Yes, it's a bit heavy on red mana, but it's a great card with all of the planeswalkers running around right now. Off the top of my head, only Jace and Garruk can survive a blow from Conflagration after ticking up once. And it takes out Siege Rhino's and other big problem creatures.

Burn Away - another card that I think is underrated. Fantastic against Whip decks.

Xenagos, the Reveler - comes in against control. The 2/2 hasty bodies are nice, and the mid-game ramp is very, very good.

Chandra, Pyromaster - I originally had Hornet Nests in the deck, and put Chandra in the board for pinging them, but I've since decided that I wanted to take the Nests out. She can still help clear blockers out of the way.

Nylea's Disciple - these may very well come out of the deck. I don't know how I feel about them since many of the permanents are red.