The budget is used to tell KoLmafia how many pulls it can use to fulfill requests to do stuff. I dont have a comprehensive mental map of all the places it comes into play, but your case is similar to the way I use it: to allow me to build/pull awesome drinks in the GUI instead of relying on crappy ones.
Consider the Booze tab. If Budget is 0, drinks in storage don't show up for me. If I set it to 2, it will show me
corpetini (2 possible, 0 current) and the Resources Used (really "to be used") shows Budgeted Pulls: 1
I don't want to spend my pulls switching from a +4.17 adv/drink beverage to a +4.25 adv/drink beverage, if I haven't pulled my +adv gear, so I want to budget 14 for incremental use and 6 reserved.
I think there are probably a few improvements that could be made, that have never quite made it onto anyone's list of things to work on.
1: since the budget is really important to the Usage panes, put it on the usage panes. It's annoying to have to go to the Storage Pane to change the usage then go back to the Booze Usage pane
2: Create some sort of default, so that we don't have to have login scripts to set it. Don't set it if you don't want to use it.
Java:
budget.setToolTipText(
"Sets the number of pulls KoLmafia is allowed to use\n"
+ "to fulfill item consumption and other usage requests");