I mostly just have two accounts: a private and a shared account.

The shared account is very simple: Every month me and my boyfriend tops it up to 5000 USD, we have a debit card to it each, and all shared expenses including rent come out of this account. By topping it off to a high number like this, we ensure we wont run out within a month, and we just use the debit card for things we need.

For my private stuff I have a credit card that I pay everything with, and I've set it up to be automatically paid off at the end of each month.

Every so often I write the expenses we've had into gnucash so I can see how much we're spending, but I don't budget in advance.

I also have a savings account with some emergency money, but I'm a poor student so I don't really have money to invest or for long term savings.