If you want to make your deck faster, it's pretty simple. Drop your most expensive cards for even more cheap ramp. They may not be exciting, but they get your strategy going fast.
Wild Growth,
Utopia Sprawl, and
Fertile Ground are really good, as they curve well into Tana and have some enchantment synergy.
One with Nature is a little spicier, as it isn't necessarily as good ramp as the aforementioned cards, but it is synergistic and repeatable once you get going.
If you want more on-theme low-CMC support,
Herald of the Pantheon &
Destiny Spinner immediately come to mind, and
Heroic Intervention is the green king of protecting your stuff (it isn't a creature, though).
In terms of what to drop,
Archetype of Endurance,
Wurmweaver Coil, and
Prodigious Growth would probably be my choices.
Eldrazi Conscription, too, maybe, but I like the spice.
I also think you might want to include
Keen Sense as another, better,
Sixth Sense effect, and
Shamanic Revelation is perfect here (post-combat, all your Saprolings are 4/4s because of Kamahl, meaning you can easily gain 20+ life in addition to the load of cards you draw).
Setessan Champion could also be cool, as she can get big and swing for a lot with Kamahl.