Sakura Tribe Elder is a good way to get lands out quickly. That was one of the "must haves" for green decks during the Kamigawa block. Personally, I like Elvish Piper, it lets you play a card from your hand for free.
I used to run a Saproling deck back in the day. I want to say Invasion block. Here are some of the cards I had in my deck:
Coat of Arms (creatures get +1+1 for each other creature with that type in play.)
Night Soil (pay one and remove 2 creatures from ANY graveyard from the game to put a 1/1 saproling into play)
Elvish Farmer (each turn put a counter on him. remove three to creat a 1/1 saproling. sac a saproling to gain 2 life.)
Rith the Awakener (If he deals damage pay 2 and one green to choose a color. Put a 1/1 green Saproling into play for each permanent of the chosen color)
Saproling Symbiosis (put a 1/1 saproling into play for each creature you control)
Sporogenesis (each turn put a counter on a non-token creature. When it goes to the graveyard you get 1/1 sparolings equal to the number of tokens. This effect multiplies if there are more than one Sporogenesis in play.)
Abundance (when you draw choose land or non land. keep drawing until you find a card of the chosen type. Put it into your hand and put the rest on the bottom of your library in any order. *Note - if you don't have the kind of card you choose in your library, you can reorder your deck however you want and set yourself up for the win.)
Elfhame Sanctuary (you can either draw like normal, or search your deck for a land during your upkeep)
Verdeloth the Ancient (Kicker X, Treefolk and Saprolings get +1+1, if you paid the kicker put X 1/1 Saprolings into play.)
Nemata, Grove Guardian (tap 2 and one green, put a 1/1 saproling into play. sac a saproling, all other saprolings get +1+1 until end of turn)
I realize you're playing mono-green, but if you have Birds of Paradise, Utopia Tree, or even Channel the Suns, Rith will come out pretty easily. (Or you could use that Piper I mentioned earlier.)
Here are some cards to help speed your deck up:
Overgrowth (enchanted land produces an extra two green when tapped)
Scouting Trek (search for any number of lands. Shuffle your library and put the lands on top in any order)
Summer Bloom (play up to 3 extra lands this turn)
Sylvan Scrying (search your library for a land and put it in your hand)
Untamed Wilds (search your library for a land and put it into play)
Wild Growth (enchanted land gives you an extra green mana)
A good way to cycle through your deck is the Psychothrope Thallid/ Saproling Cluster combo. Thallid says sac a saproling to draw a card. Cluster says discard a card to create a saproling. As long as you can keep tapping one mana for each time you want to do it, this can help you get what you need quickly.