To unlock videos:
One can be earned from collecting all tapes in one night. I believe there are six tapes. You get a notice when you have them all.
The rest can be earned by surviving a night with a plushie on your desk. One video per night per character plushie, up to two videos each. At least, I believe that is the current count.
(There is one video that I don't currently know how to get. You used to get it by playing the mini-game on the main menu in previous builds.)
To unlock figures:
You have to find crystals while playing to spend them at the gacha machine from the main menu, gallery section. The crystals are small and bright pink.
From TheThunkening:
I got the last poppi video from the car mini-game when it popped up after a death, so it might be a random death game thing.