Milk Supply

I haven't had the greatest milk supply since having my little one 6 weeks ago. He is gaining weight just fine so I know he is getting enough but I don't have much left over to pump when he is done. I have supplemented a few feedings a day with formula and just pumped so I can have some saved up in my freezer for when it is needed! So my question for you mamas is: how much milk do you have stocked up and when do you know you should use it? I don't want to start using it and end up going through it all right away and not being to keep up with restocking!