Efficient Elemental Manland Creation
If you want your lands to specifically have the "elemental" creature type:


Liege of the Tangle


If you don't care what creature type they are, as long as they're creatures:


Jolrael, Empress of Beasts
Life
Living Plane
Natural Affinity
Natural Emergence
Nature's Revolt
Rude Awakening


If you only need a single type of land to be animated:


Forests


Ambush Commander
Living Lands
Thelonite Druid
Life and Limb

Swamps


Kormus Bell