Student or Learner
Suppose you're on a guided tour in a town. Can I say "I have 25 dollars of the walking around money" just to say that you will spend them on whatever you want?
I have to disagree slightly with riquecohen, the phrase "walking around money" is familiar to me and it can mean more or less what you said - money to buy things you need or want when you are out and walking around. It is street slang, I think.
It also has a meaning in American politics where it refers to a "slush fund".
Obviously, not all native speakers will understand you, so use it with caution.
ETA: "spending money" is a good general phrase that most people will understand.