Release the Gremlins : Sorcery, casting cost of X generic, X generic, and one red mana
In formats like Pauper, where all dual lands are tapped lands, they are one of the best land cycles in the format, with a whole deck (Skerd) being built around them
This has exploit, which is a may effect
These are the free sacrifice outlets in this deck: Altar of Dementia Carrion Feeder Cartel Aristocrat Spawning Pit Viscera Seer Priest of Forgotten Gods (must tap Priest of Forgotten Gods but should probably be done at sorcery speed unless you have an instant to use with the 2 extra black mana the ability will give you) While these are probably your best targets to sacrifice a creature, there are a couple more
There's also Kirri, Talented Sprout as a plant/treefolk typal commander, though the red in it color identity doesn't do much for you if treefolk creatures are your focus
Green leverages its creatures with cards like Shamanic Revelation and the game-swinging Rishkars Expertise