Here is an older post on Actrium. Not sure if you've seen it already:
http://www.pets.ca/forum/showthread.php?t=37773
I understand what you are saying about your budget but if you were to consider a better quality food, your dog would eat less, poop less and a bag would therefore last longer. So, you might even end up spending the same amount on a better quality kibble. Not to mention a healthier dog which likely means less trips to the vet which add up in the long run.
I have heard that Kirkland brand at Costco is a decent price for the quality if your main goal is to save money.