Can't tell you which version or edition, not enough information. Review the documentation on MSDN, look at the features in each edition and version and see what you need and what you can afford.
SQL has Enterprise, Standard and Express as the main editions for 2012. Review what they offer, see how much they cost, pick the cheapest one that has the features you need.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
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