Get into the notation and tensor formalism of raising and lowering operators, etc. It really helped make some of the results more clear to me, just as <bra/ket> helped with QM.
Or are you doing high end astronomy or building a back yard Wave detector? That would get truly expensive!
But yeah, thankfully on that front I am not at the experiment stage yet:D I think I need more money for that.. so far.. just a whole lot of books.