Green has enough powerful options in Standard that you don’t need access to any other colors to build a competitive deck. With some of the best creatures in the format and plenty of ramp you have everything you need to win.
Hour of Promise is a premier ramp spell. It’s on the expensive side, so you’re going to want ways to use all of your extra mana, but the rewards are big. This single-handedly ramps you up to the city’s blessing without the help of any other spells. You’re going from five mana sources up to seven and you even get a pair of Zombie tokens out of the exchange. 4 power for 5 mana is already acceptable, but getting multiple lands, many of which may have extra utility, is extremely powerful.
Wayward Swordtooth plays right into this plan. Not only does it help you ramp, but in combination with an Hour of Promise and a single Desert in play, you have an undercosted 5/5 creature that immediately loses its one drawback.
When Hour and Swordtooth aren’t enough ramp, you go straight to Druid of the Cowl. Llanowar Elves is going to slot in real nicely in this deck! Rishkar, Peema Renegade gives you more ways to pump your creatures while also providing a ramp from 3 to 5 mana to cast Hour. In the later stages of the game where many of your creatures will naturally already have +1/+1 counters, Rishkar will give you a ton of mana ramp to use on your mana sinks.
The best of these mana sinks just happens to come with its own counters. Walking Ballista’s stock is back on the rise with red aggro decks, U/R Gift decks, and Glint-Sleeve Siphoner being popular options. Rishkar can put additional counters on your Ballista and this is a great way to use excess mana throughout the game. Ballista doesn’t need to rot in your hand in order to take advantage of your ramp as you can either cast it for absurd amounts or get it onto the battlefield to add counters later. This isn’t your only mana sink, however, as Rhonas the Indomitable takes your excess mana and turns it into trample damage.
Jadelight Ranger and Merfolk Branchwalker provide efficient creatures that help you make more land drops and filter through your library for key cards. They also play well with Rishkar as creatures that will often naturally have +1/+1 counters and can tap for mana.
Along that same idea, Narnam Renegade will often have a +1/+1 counter should you want to wait, but it’s also an efficient creature that can trade up with the biggest threats in Standard.
All of these creatures are nice, but they can get brickwalled as ground attackers. Going to the sky in Vehicles is a great way to push your edge in Standard, as well as playing around sorcery-speed removal and sweepers. Skysovereign, Consul Flagship hits hard in the air and can help eliminate problematic creatures and planeswalkers. Heart of Kiran can come down early and allow your various explore creatures, Rishkars, and inactive Swordtooths to get in for 4 damage in the ship. This is also a great way to effectively give your many creatures haste by letting them crew and get in for damage immediately.
Here’s a card I haven’t seen before: Mouth // Feed. A 3-mana 3/3 Hippo is a fine rate, but this is a great way to cash in on having both a ton of creatures and plenty of mana ramp. Feed can pretty easily draw a full hand of cards in this deck and the explore creatures can put it into your graveyard to aftermath for value. With Rishkar to pump your team, plenty of 3-power creatures, and Vehicles that you can crew (to both draw a card off of the Vehicle itself and the creature that crewed it), Feed can provide card advantage this deck can really take advantage of.
Desert Green is a sweet deck that attacks the metagame from a different angle than any other deck I’ve seen. Combining raw card advantage, mana ramp, and some late-game mana sinks can provide an advantage that opponents aren’t ready for!