Casual BEASTS (Casual)

At the beginning of a match you mostly want to play Green Sun's Zenith into Dryad Arbor.

Wirewood Savage helps you draw additional cards when playing a beast creature (Also Garruk's tokens), Krosan Warchief makes your beasts cheaper to play which makes you have cheap card draw combined with strong beast bodies.

Birds of Paradise and Dryad Arbor are good for mana ramp and are an eventual body for emergency blocking and also super potent with Craterhoof Behemoth.
Explore gives you more card advantage while playing even more lands.

Krosan Tusker can either be played as a creature but in most cases you want to cycle it to draw a card and have an additional land on the field.

Garruk is very good to have many beasts (and cards with Wirewood Savage), but also very strong when untapping Forests for expensive beasts.

Mold Shambler is a very good (and cheap with Krosan Warchief) body (and a card draw with Wirewood Savage) and an optional removal.

So the main goal of this deck is to have many (strong) creatures on the field and either hard cast Craterhoof Behemoth from your hand or Green Sun's Zenith into it and powering up ALL your creatures and providing them the trample ability. Due to its Haste it attacks as well and in most cases enemies end up with over -100 life after the killing blow.