I want to buy a cloud server，and what is the basic system requirements?

I want to purchase a cloud server and didn't know how many nodes to buy. Each node include a 0.6GHz CPU, 376RAM and 15GB disks.

I want to have a omeka for 50-100 people to use.And may be 300 people to use in the future.
Is there any advices that how many nodes need to buy.
thanks.

Please take a look at the example server requirements we have provided in the Preparing to Install section of the Documentation: http://omeka.org/codex/Server_configuration