When applyig to colleges on the commonapp is it worth it to fill all ECs slot even if some are pretty low tiers and I have nothing else to put in it?
I agree with @agupta22 that in this case quality is probably better than quantity. It's going to look better for you to have only 3 ECs you were very involved with on your application compared to 8 ECs where you didn't participate too much. If you joined a club in a topic you are only semi-interested in and only went to the meetings once a month, it's probably not worth putting on your application.
Another way to think about this: the more "fluff" you add to your application, the more you take away and dilute the value of the ECs you actually care about and want admissions officers to notice.
To keep this community safe and supportive: