When it comes to buying the right film I am no help. Maybe we'll get a Pro Film Photographer to speak up and give us all a lesson. Volunteers?
What I do know, especially with Nikonos cameras is that your film speed affects focus. The higher F-stop your lens is set at increases the chances of sharp shots. But the higher F-stop means less light is reaching your film. So you have to either slow your shutter or have a faster film.
My recommendation to new Nikonos recipients is to start with 400 ISO. The cheap stuff you buy at Walmart.
f22 allows the least amount of light to reach the film (hence the small opening). At f22 EVERYTHING will essentially be in focus (assuming you don't have camera shake).
My cameras are usually at f8 or 5.6. This gives me a 2-4 foot window on focus. Its very situational and takes practice to master. These are not digital cameras where we can spray and pray that one of the 1000 shots turns out. I plan the shot in advance.
If I'm shooting surf, I set my camera where it needs to be then wait for the rider to come to me.
If I'm shooting landscape, I turn the focus to ∞ and click my lens to f5.6 or 8 (these tend to be the sharpest).
Sometimes, even with 400 film we need more light, f2.5 is available. There is a 9 inch window of focus. So grab the tape measure and get your distances right..