One thing to be careful of is that a high ISO means your pictures will have lots of noise (grain) - it's the same as buying film. It's best to stick within the range of 100 to 400 ISO.
Interesting that you recommend 100 to 400 - I never shoot anything in that range.
I use mostly 800 to 1600 and don't really notice that much noise - I might experiment with the slower film speeds and see what sort of results I get.