This is going to depend on how big and how many journal receivers you have and how big and how many spooled files you have.
Generally the journal receivers take up more storage than the spooled files, especially if they haven’t been removed for some time.
Some good tools to use to help you find the areas of biggest impact are
RTVDSKINF *SYSBAS – This will output to a file QAEDISK in QUSRSYS. Run a file that totals library sizes and counts objects.
You can also output the results to a file including the run date and append to it each day to monitor trends.
This will allow you to identify the objects and files taking the most space.
For many modern systems, the best way isn’t spooled files nor journal receivers. Neither of those should ever be a problem in the first place. There should not be any significant volume of spooled files nor journal receivers eligible for deletion in the first place.
For many modern systems, unused or obsolete streamfiles are where the most wasted space is.