If you don't put it in a bank account, then assuming no magical tracking, you could spend lots of money so long as you don't reach a point where anyone starts asking "Hey, where did you get all this expensive stuff?"

Since the wizarding world has so much smaller a population than ours and seems to be quite class stratified, it's quite conceivable that every person who's supposed to be really wealthy is already known and identifiable, and any Joe Shmoe who tries making a thousand galleon purchase is instantly flagged as suspicious.