As long as you make at least 1 post in a period of 2 weeks and your post count is greater then your activity score your Activity will increase every 2 weeks bringing you a bigger rank
Brand New: 0 posts, gets 1 gold coin under his name.
Newbie: (none), gets 1 gold coin under his name.
Jr. Member: activity: 30, gets 1 gold coin under his name.
Member: Activity: 60, gets 2 gold coins under his name.
Full Member: Activity: 120, gets 3 gold coins under his name.
Sr. Member: Activity: 240, gets 4 gold coins under his name.
Hero Member: Activity: 480, gets 5 gold coins under his name.