Math / theory for real-world prioritization / allocation

The problem of managing scarce resources is common to many video games that require "building", to complex businesses, and to scheduling one's time. (This post is prompted by that last one, but clearly spans a wider scope.)

To give everything to the single activity that provides the most gain, one must have a comparative advantage, and trade with others for what else is needed, which is not always possible. And taking a broader view, it makes for a very fragile system.

Giving a completely equal amount of time to each activity is generally incongruent with the relative difference in need or value for the activity.

What concepts, papers, frameworks, etc. exist to help manage this type of problem?

For a more concrete example, imagine (perhaps little imagination required!) being a young, independent adult, trying to "maximize value" across the domains in their life. This appears to be a rather vague intention, which is itself at least some component to this problem. Even if we were to assign some number of "utilitons per hour" to each activity, and perhaps a "domain flavor", maximizing "value" intra-domain may become more clear (though it's not obvious that this is necessarily true, unless one allows for an arbitrarily high number of "domain flavors", which, taken to the extreme, is effectively to have none at all), but the problem of managing inter-domain "value" remains. Some activities may be subject to satisficing, but others have "value" which increases at an uncertain rate per hour applied towards it.

I know that something in the area of packing/allocation/knapsack/"scheduling" problems would be relevant, but there is a lot of material to sort through, and it is typically very abstract. Does anyone have more applicable resources or explanations that may be useful here? Thank you.