Green is great because it has plenty of low-mana costing monsters and "search your library for a basic land card" spells/effects. It's usual effect is to outnumber your opponent while creating a big wall of defenders (unless....your opponent has cards with trample).
I suggest looking into making an entire elf deck: composed of nothing but 1 or 2 mana costing creature cards. Elvish Berserker and Thornwield Archer are good ones thanks to their effects relative to their mana costs.
Might want to hide a few spiders in there too, it helps to have defenders against fliers.
Kavu Primach can easily come onto the field as a 7/7 for only 4 mana since it has a convoke cost; Nactyl War-Pride can create copies of itself when a player defends it... and they MUST defend it every time it attacks...with only ONE creature; and Baru fist of Krosa is excellent for his ability because with a pure green deck, you'll be spewing forests everywhere, all your creatures get +1/+1 and gain trample thanks to him!
I know what your thinking though: With all of this mana, I want to summon some bad-a** strong creatures, I've got the mana to do it so why shouldn't I? If that's the case then you should switch to red, green is created purely for outnumbering your opponent and being able to swerve across defending creatures with your sheer numbered assailants to diminish their life to zero. Better yet, try mixing with red so you can create an outnumbering strong creature power-house!