Most of the counters are not available beyond 1 hour. vSphere is not a performance monitoring tool, it's more like a platform administration tool. You should be using the bundled vCenter Operations (the edition bundled with vSphere is free. Certainly, it consumes resources too) for performance management and troubleshooting.
I'd watch for Contention first, then Utilization. This is because high contention is bad, regardless whether you have high or low utilization. On the other hand, if you have high utilization, but low contention, that means your investment on the infra is being used well :-) You may need to buy more infra, but that's a Capacity Management discussion, not Performance Management (I agree they are the same topic on 2 different time scale).
For utilization, I'd watch for the following:
- for VM: Usage (which is Active)
- for ESXi: Usage (which is Consumed) and Active
I'm tracking Consumed at ESXi level as it shows what was active before.
I won't worry much about Granted once I track Consumed, as Consumed = Granted - Shared.
Hope that helps