Two.
I’ve got one which is strictly for emergencies.
And I’ve got one that’s attached to my mortgage offset account and I use for day to day expenses, then pay off before the end of the month. Basically:
my entire salary gets deposited into an account attached to my mortgage. When interest is calculated, it’s calculated based on what’s in the offset account as well (more money = less interest).
I use a credit card that has an interest free period for my expenses through the month.
before the end of the month, I transfer the payment for my mortgage from the offset account to the mortgage account.
before the interest free period is up, I pay off the credit card.
Rinse and repeat next month. The aim is to keep as much money in the offset account as possible when interest is calculated, but pay off the credit card before the interest free period is up.
If I need cash, I can draw it out of the offset account. But anything that doesn’t need a cash payment gets put straight on the credit card.