Feeding it what you want it to gather has NO EFFECT on its father rates. These are determined by the additional level granted every level to increase your moschops' gathering efficiency of your chosen resource.
So I tamed one on my 2nd day on ark. It was a level 90. It is definitely helpful for people just starting out because if you set it to wander it collects a good amount of fiber, berries, wood, and thach. I recommend it to anyone starting out because it can be a great help getting those resources that you need.