This is a basic green devotion deck. It's pretty good at playing up the various strengths of green, i.e. creatures, and gives good examples of what i feel to be the most basic things in green, such as efficient beaters, fighting, and some basic ramping.
Cards i recommend using if you go to modify this deck:

Rampant growth/harrow/explosive vegetation/cultivate: green is very good at land ramping.

Any planeswalker with the type Garruk

See The Unwritten

Hooded Hydra, or any other creature with the type Hydra

Collective unconscious/ shamanic revelation. green is amazing at card draw, especially when it comes to creatures