In general, the requirement for the machine greatly depend on your data processing requirement. If you have data size of 100TB, you need at least have enough disk space for storing that data and maybe the same amount for GraphLab Create as 'cache/swapping' place and more for other usage (log, temporary data, etc.).
Regarding CPU the more, the powerful the merrier. GraphLab Create is smart enough to take advantage of all available cores to efficiently process your query.
Regarding RAM, again the more, the faster the merrier, and you will need to use graphlab.setruntimeconfig() to be able leverage the memory most efficiently.
Ubuntu 14 64 bit is good.