Since the graveyard is often like a second hand for many decks in Commander, denying your opponents access to it puts you at a distinct advantage
Rakdos's Return provides all that value while scaling with the game

Astrologian's Planisphere Rarity: Rare TYPE: Artifact SUBTYPE: Equipment CMC: 2 Mana cost: USD: $4.34 EUR: 3.90 TIX: 0.00 EDHREC RANK: 5649 Job select (When this Equipment enters, create a 1/1 colorless Hero creature token, then attach this to it.) Equipped creature is a Wizard in addition to its other types and has "Whenever you cast a noncreature spell and whenever you draw your third card each turn, put a +1/+1 counter on this creature." Diana Equip Astrologian's Planisphere Rarity: Rare TYPE: Artifact SUBTYPE: Equipment CMC: 2 Mana cost: USD: $0.29 EUR: 0.29 TIX: 0.09 EDHREC RANK: 5649 Job select (When this Equipment enters, create a 1/1 colorless Hero creature token, then attach this to it.) Equipped creature is a Wizard in addition to its other types and has "Whenever you cast a noncreature spell and whenever you draw your third card each turn, put a +1/+1 counter on this creature." Diana Equip Auron's Inspiration Rarity: Uncommon TYPE: Instant SUBTYPE: - CMC: 3 Mana cost: USD: $0.17 EUR: 0.08 TIX: 0.03 EDHREC RANK: 18422 Attacking creatures get +2/+0 until end of turn

Cultivate always has a place in green decks, and heres the list of other ramp cards in the deck, to get more card draw, forests, mana, or creatures onto the battlefield: This ought to get the deck moving out of the gate
I dont know if Beza, the Bounding Spring belongs in the main deck or sideboard, but it will see Standard play
That's four by turn five with no mana used yet, you might have already completed one, Zombify