As with most saproling decks, this is about having lots of little creatures. However, there are some key combos with larger creatures that make it unique.
For mana production, there is Birds of Paradise and Viridian Emissary (which doubles as an early blocker). I previously played one Mountain which I searched for with Viridian Emmisary to help with my splashed red, but I eventually found it unnecessary as I can produce red with Birds of Paradise and the wonderful extra ability on Utopia Mycon.
To produce saprolings, there is the slow and steady Utopia Mycon as well as the once-per-turn Selesnya Evangel. Past that, there is Scatter the Seeds (which is easy to cast for cheap by convoking saprolings already in play) and Supply (which tends to be a late-game play). Then there is the mighty Mycoloth as well as Thelonite Hermit which are two essential cards to give the deck momentum. Lastly, there is Fists of Ironwood, which ends up being a late-game play on one of the bigger guys (more on that later).
For super helpful triggers, there is Juniper Order Ranger which makes all saprolings bigger, as well as Aura Shards which keeps my opponent's board cleared of artifacts and enchantments (this ability can shut down some decks). With both Juniper Order Ranger and Thelonite Hermit out, saprolings are very dangerous token creatures.
However, the real fun in this deck is the combo of + . Getting Forgotten Ancient out early and then putting all (or most) of his +1/+1 counters on Mycoloth makes for some really big saproling production. Forgotten Ancient can also feed the ever-resilient Protean Hydra (which is a non-essential card, but very fun to play) and the useful Ulasht, the Hate Seed.
Thanks for taking a look! Don't forget to +1 if you like what you see.
Current list of subbed cards need: 1x Nourish , 1x Knotvine Paladin , 1x Selesnya Evangel , 1x Tribal Forcemage , 1x Pollenbright Wings , 1x Viridian Emissary , 1x Verdant Embrace fillers: 1x card:Heroes' Reunion, 1x Mycoloth , 1x Juniper Order Ranger , 1x Rampant Growth , 1x Saproling Symbiosis