Tarsi
Late fees and interest are avoidable. Most people just lose track of the date.
A credit card is close to free money if you clear the statement balance every month, and expensive the moment you do not. The difference is almost never the limit. It is the date.
Two things are worth knowing by heart: your statement date, when the balance is struck, and your due date, when it must be paid. A purchase made right after the statement date gets the longest interest-free run.
Paying the minimum keeps the account in good standing and the debt alive more or less forever. Treat the statement balance as the real bill.
Put every card in Tarsi with its due date and let the reminders do the remembering. The payments-due timeline shows what is landing before your next payday.