What should the commerce student do after 12th class except CA?
There are other options to pursue apart from CA.
You could choose from other professional courses like CS, CFA, CMA, CFP, FRM.
Or if you do now find interest in any of these you could go for a BBA, take part in various activities, do certification courses like the nose and build up your profile. Then in your 3rd year you could start preparing for CAT, XAT, NMAT and other MBA entrance exams.
Hope this helps. Do feel free to ask further questions.
All the best!

Happy to help. All the best in your future endeavours!