Load ISO 100 film and you won't have problems with too much light ...

The polariser will reduce light by 1.5 - 2 stops but it changes saturation & reflections as well. In bright sun it's very easy to overdo the effect. Personally I wouldn't bother. Yes, it does darken a blue sky (no effect on a cloudy one) but the effect can look very strange with wide angle lenses.

As for the ND grad - if you need it because of contrast between the land & sky then it doesn't matter what the light level is - in fact in my experience you're more likely to need an ND grad when shooting in twilight!