Prepping physical ,audio and video props, is quite time consuming, but back when we had more time (before jobs, wives, etc), we often made props as clues or distractions/red herrings.
When I worked for a book binding company some years ago we used to make spell books, and journals etc using scrap leather/pvc scuffed up, cheap metal hinges etc. I leather bound
a copy of Runequest for myself too.
My local used-book shops often have "dusty old tomes" fairy cheap.
Foreign language books, for example are great for code key books for spy/military games, leaving margin notes as clues, and being dirt cheap, its not an issue to underline and scribble in them, burn them up, damage them etc.
Look out for old photo albums, journals etc too.
Free software like Audacity (
https://www.audacityteam.org/ ) can be used to good effect to record radio transmissions, and add static,white noise etc to them. We would sometimes get an extra player in to "guest" as npc radio contacts etc, either live or pre recorded before the session, or use a voice changer like the Tomorrows End gm does when playing their driver (who never seems to leave the cab of their vehicle and always talks over the intercom lol).
I bought an old pile of thick old books for a game some years ago, and made a cut out in the pages of one of them to hide a small object. I had set up a table with items the players had found in a trunk and left the books piled up with other junk, including a couple of red herrings, old cinema ticket, money, wallet etc.
They picked a few of the books up, but managed to miss the one with the hidden object inside but chased a red herring for 2 hours... oh well. lol.