You should enable FileVault encryption, then erase the drive the standard way. Erasing the drive the standard way erases the metadata, but not the actual files, but if the drive is encrypted before it is erased, someone tying to recover the erased files would just find jibberish.
The term for this is cryptographic erasure and the huge benefit of this is the erase is basically instantaneous when you wipe the keys that can unlock the data.
