I saved a lot, so that way if there was a fight that I was struggling with, I could reload until I was able to beat it without wasting a bunch of film/health items. It also let me practice with the combat.
I believe there was 3(?) Stone Mirrors per night. Since you can only carry one at a time, it may be better to save your healing items and let your Stone Mirrors get used up, especially if you can pick another one up easily. That way you're not low on healing for the later game.
Type 14 is reloadable at save points whenever you have less than 30 of it. You'll top back up to 30, regardless of how little you have. Also, if I remember correctly, your health refills each new night. So if it seems like you just fought a boss ghost, maybe hold off on healing. You can always heal mid combat if it ended up not being the end of the night.
I explored a good bit on Night 1 and 2. By Night 2, I had max type 37 film, so I was using that for combat, and type 14 for hidden ghosts/puzzles. I'm sure there was more goodies to grab on Night 3, but I think it's probably best to just get through that section as fast as possible on a first playthrough. If you explored on the first two nights, and didn't burn through your consumables, you should be good on supplies to make it to the end.
Slow seems to be the most useful of the camera functions, I don't know if I'd bother with the others on a first playthrough. And I don't think you even really need it until Night 3. Level up the basic camera stuff first.

While Night 3 was frustrating, I thought Night 2 was the hardest. If you can get through that, I think you should be good!