Selvala is awesome! Your first goal is to find a place for Umbral Mantle and Sword of the Paruns though.

Ah yeah I need to find a spot think about switching out Snapping Gnarlid and Fang of the Pack

Hydras! Primordial Hydra Vastwood Hydra etc.

What would I take out for those

I definitely like this. I also sometimes play a Selvala deck, except its more eldrazi centered. I do like some cards that i havn't thought about, such as Gaea's Herald and Wirewood Lodge.

Herald is nice for me especially playing against 3 heavy control decks sometimes plus, you can make friends even if you are the combo deck!

Just a few suggestions:

Nykthos, Shrine to Nyx: Extremely good for mono color strategies

Utopia Sprawl: You run enough forests to make this work

Garruk, Caller of Beasts: Fits the name, just a really good way to find creatures

Llanowar Elves, Elvish Mystic Ramp creatures that you can grab with Yisan early on.

Avenger of Zendikar: Can't go wrong with those 0/1 plant tokens! Nissa, Voice of Zendikar also synergizes well with AoZ, but might not be worth the include just because of that, as she dosent really help early on.

Dropping Soul Swallower and Spawnwrithe but what else?

Green is almost indisputably the best card draw color in EDH but your missing out on it. Zendikar Resurgent, Shamanic Revelation,Soul's Majesty,Soul of the Harvest, and Regal Force are all worth playing over stuff like Feed the Clan, and Harmonize. You may know the combo between Selvala and Omnath but basically she doubles the amount of mana in your pool with him out. If you have Temur Savertooth out, you can bounce and recast Omnath repeatedly for five mana to keep redrawing from Selvala's trigger too.

Totally Forgot to put in Majesty My bad um Soul seems meh honestly so does revolution however the rest are going in

Soul of the Harvest is amazing. It rewards green decks for doing what they already want to do, which is play creatures.

This green deck is looking to get infinite mana actually via 2 ways staff of Domination or umbral mantle the main plan is get sel out get something with power 4 or greater then win