We recommend the 2 Month frequency for $19 on the previous page. 

This plan is the most versatile for single members and couples. It works out to only $9.50 a month (or $4.75 each if you're sharing). 

If you're not sure where to start, start with the 2 month frequency then adjust your account before your next shipment if you still have some left. Otherwise you might wait a month before getting more.