How should heads of music manage their departmental budgets?
This is one area which you must, at all costs, get clear answers on. If there seem to be any grey areas about the money you have and what you spend it on, hassle your line manager until you get unequivocal information. You simply have to be in full possession of the facts before you can decide on the best plan for making the most of what you’ve got.
It is almost certain that whatever budget you are given will have to cover reprographics and spending on instruments and accessories for the department. Schools vary a great deal, though, on what else might be included in your financial remit.