What type of standard deck can be made with mono green that's competitive yet on a budget
Mono green devotion could be good. Boss sligh is 20-30 dollars and is a mono red teir 1 deck..
Is there anything else besides devotion for green
Not really...
How about modern?
Look up polishtamales on tumblr. He has articles about a modern mono-green deck
Mono green monsters/enchantments is about the most competitive one. It splashes red for bte and Xenagos the reveler and for now domri rade
I admit I play pretty casually in modern but...
Elves!
There are some great ways to lay the stomp down with elves.