I was lucky and I’m still grandfathered into gmail for domains for free, but I only get 15GBs of space including my Gdrive and photos. So I’m always trying to keep my attachments small in gmail. Here’s a quick tip to search for large attachments.
In the search bar in gmail enter
This will show you emails with attachment greater than 5MB. You can change the number higher or lower depending on the size of attachments your looking for.
If you like keyboard shortcuts, take a look at this infographic