I was thinking about how I am running manufacturing in Manu Fortius. I am working with a small amount of capital and reinvesting as I manufacture and sell items. The balance is always increasing, but I have to pay close attention to the cost of materials. Normally, when I manufacture for myself, I have at least a few billion in liquid ISK to cover my production. I also have a large reserve of resources and components. When I do runs, i might do a mass run of the components (more than I need) and then stockpile them. I can still get an accurate cost/manufactured item, but it is generally less of a concern. Manufacturing with a limited budget does create an issue. Often, production runs cost close to what is available in the till. I try to run as many jobs as possible so that I can maximize my travel and market order monitoring tasks. Sometimes this leads to using most of the wallet division ISK. When that happens, you are at the mercy of the market and items must sell before you can manufacture more. If you have a lot of capital, this really doesn't need to be a concern. Micro-managers might find that statement strange.
Currently, I am buying everything I need for that production only. I am not over-buying or producing surplus components. I am watching things down the .01 ISK. Once you get around 250 - 500mil ISK in the wallet and you are manufacturing T2 frigates and modules, you might be able to begin a stocking program on your commonly used minerals, PI and components (or raw moon materials). If you are sticking to a certain item line (say making armor modules), you can probably stockpile robotics, construction blocks and armor plates. What you do and when you do it is based specifically on your manufacturing plan. Right now, I am fine with buying what I need. It can become cumbersome when you start having to run around or place buy orders and wait for them to be filled. Planning your production well in advance can mitigate much of your downtime.
If you have any questions on how you might tackle a supply problem, let me know in the comments and as always, fly safe-ish.