Backups should protect the information required to restore the service, including website files, databases, application configuration and any uploaded content that is not stored elsewhere. The correct frequency depends on how quickly that data changes.
What to consider
A static business site may tolerate a daily backup, while an ecommerce database can change every minute. Retention should also account for problems that may not be noticed immediately, such as malware or accidental content deletion.
Keep important backups separate from the primary server and test restores periodically. A backup is valuable only when it can be recovered within the time the business expects.