This combo is pretty cool.
Devoted Druid 1G
elf druid
tap add g to your mana pool
put a -1/-1 counter on devoted druid untap it.
0/2
Quillspike 2 b/g
Beast
b/g remove a -1/-1 counter from target creature you control, quillspike gets +3/+3 until end of turn
1/1
First tap the devoted druid to add 1 g to your mana pool, than put a -1/-1 counter on the devoted druid to untap it. Than use that green you produced from the devoted druid to activate the quillspike's ability and giving it +3/+3 until end of turn by removing the -1/-1 counter from the devoted druid. Repeat as you like.