Sachi, Daughter of Seshiro

Other Snake creatures you control get +0/+1.
Shamans you control have "{T}: Add {G}{G}."

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

{1}: Target creature you control has base power and toughness 7/7 until end of turn.

Treefolk spells and Shaman spells you cast cost {1} less to cast.

As long as Centaur Omenreader is tapped, creature spells you cast cost {2} less to cast.