That would be "bruker penger".
"Å tilbringe" is related to being or staying somewhere.
From an earlier lesson - "Gutten bruker mye tid på badet" - are "bruker" and "tilbringer" interchangeable in the context of being somewhere or is there a way to know which one is the most suitable?
Yes, both would be appropriate in that context, with "tilbringer" being the more formal option of the two.
How do you mean? It applies to time in the sense that you can be spending time somewhere. However, if you're spending time on something, then you need to use "å bruke".