Which course to take in Commerce?
If you mean by subjects to choose in 11th Commerce, then, taking maths, business studies and economics along with accounts could be a good combination.
Computers is an option, but that can be taken only if you really like or planning a career in it. If you need, you may always pursue it after 12th since the eligibility to take BCA or BSc IT or Comp. Science is 12th pass with Maths.
Accounting & Finance, along with economics and business studies makes a really great combination. Maths is always a great choice and scoring too. You would be doing a lot of number crunching in your management studies later, so, these subjects combinations could be of great help. Economics could be a bit of theoretical too, but its a great tool to understand how the economy works and plan your business strategies around it.