If you're not used to budgeting just write it all down, everything you earn and everything you spend. Keep a certain amount separate as an emergency, for food or shelter. Most of the inns are 500P or less make sure you have enough set aside to at least cover a few days since every job only pays on Fridays.

When I just got here I stayed in towns for a few weeks at a time to earn money, and since you can heal your pokemon at the Pokecenter you don't need to spend as much on medicine.