What cheap yet very useful things have made a substantial change and improvement to your life?
For me it has always been USB flash drives. I'm scared of getting ransomware'd one day, but I am safe in the knowledge that I'd have to have every thumbdrive I own plugged into my PC for some real damage to happen. They are a lifesaver, and they get cheaper every year too!
Google Drive's internal search is not good enough when there are 100s of documents with similar titles, so I try to maintain a consistent naming convention "{yyyy-mm-dd} {summary of document}". Electronic documents (e.g. bank and credit card statements) are downloaded as PDF and uploaded to the same Google Drive folder hierarchy.
The originals go into a set of 12 file folders labeled "Jan" to "Dec". The folders become a ring buffer. Every month, I empty out the upcoming month, by shredding the originals from 12 months ago. I got rid of a 4-drawer filing cabinet by incrementally scanning the original paper documents over several weeks.
(Edit: fix typo)