I personally love playing green, this is my current deck list that I've been climbing the ladder with in Bo3 and Bo1. It is both Aggro and Midrange in style. Its main weaknesses are Red/Raktos Aggro and Blue Countermagic, which I've somewhat countered with the sideboard.

Deck:

• Pelt Collector - Great Starter, grows well with the 2,3,4 drops in the deck
• Growth-Chamber Guardian - Solid 2 drop, combos well with Vivien and Great Henge
• Paradise Druid - Ramp, plus access to Black Mana for Sideboard, doesn't get insta-shocked like other rampers
• Lovestruck Beast - Solid Blocker versus aggro, quick ramp to a 4th turn Great Henge
• Thrashing Brontodon - Solid Blocker versus aggro, Removal for Enchantments (Fires of Invention, Ethereal Absolution, The Great Henge) and Artifacts (Embercleave, Lucky Clover, Witch's Oven)
• Questing Beast - Solid Card, Anti-Planeswalker
• Vivien, Arkbow Ranger - Combos with Growth-Chamber to pull more, gives trample to cut through, removes (fights) creatures and can be -5 to pull Forerunners out of the Sideboard
• Nissa, Who Shakes the World - Beast of a Planeswalker, Ramps and applies pressure, allows Serpent and Hydras below to be massive
• The Great Henge - Once you can play this safely, do. It's hard to lose the game once in play, with additional 2 life, 2 mana, +1/+1 tokens (that combo with Growth-Chamber) and card draw
• Stonecoil Serpent - Reach for flyers, Trample to close, can be played early for aggro, protection from multicoloured surprisingly useful (Mortify,Assassin's Trophy,Bedevil,Tyrant's Scorn. Combos with Nissa
• Voracious Hydra - Creature removal or Huge Creature, with trample. Combos with Nissa

Went for 4x Castles, just remember to use them if in play. The lifegain from Gingerbread is useful, don't play 4 copies though

Sideboarding:

• Versus Aggro: Remove Nissa x3, Add in Gilded Goose x3 - Blocks 1/1's and generates life tokens to keep you alive
• Versus Enchantment / Artifact based decks (see Brontodon notes above) - Remove Lovestruck, Serpent, Hydra (depends on who you are playing), Add in Return to Nature x2 and Assassin's Trophy x2
• Versus Planeswalkers / Difficult Creatures - As above with just Assassin's Trophy x2
• Versus Blue Countermagic (hardest Matchup) - Remove Serpent x3 and Hydra x4 (you'll sink massive mana into something that will get countered + they don't work with Arkbow), Add In Shifting Ceratops x4 (obvious) and Vivien's Arkbow x2 (Milligan to get this in your opener and jam down before it can be countered, then play all your creatures this way)
• End-Raze Forerunners - This is in the sideboard to finish a game through -5 on Vivien

Maybe:

During play testing there are a few cards that are noticeable mentions:

• Biogenic Ooze (as Main Deck) - Great but went for Serpent in the end as more versatile, and has reach/trample. Also Ooze gets insta-shocked
• Evolution Sage (as Main Deck) - With the amount of +1/+1 tokens in the deck, Planeswalkers and Vivien's +1 this is great, but ultimately went for Brontodon instead, you could sub this in for fun though
• Cindervines (as sideboard) - Ultimately nothing for than an annoyance for most decks
• Rhythm of the Wild (as sideboard) - Vivien's Arkbow is better and you can get it off quicker before it itself is countered

Play notes:

• Always play Nissa or Henge if you can
• Use Vivien's +1 on Growth-Chamber
• You don't have to always fight Hydra, doubling the tokens can sometimes win the game quicker

Any questions please ask!