Hi Noundla Chandrasangna!

Congratulations on completing your 12th class. This is the peak time to make decisions regarding your career. It's a good thing that you have chosen to become an IAS. The biggest confusion now is whether to go for graduation or go for coaching. But, that's alright, you need not to worry. This is the point where most youngsters get confused. 
So, what I would like to suggest you is that you better pursue graduation in any field first, it could be engineering, any degree, etc. Why I am asking you to do this is because, if at all, by chance you are not able to clear the exam for IAS, you will at least be left with a graduation certificate that will help you land in other jobs for the time being until you figure out your next steps. That is why it would be better if you take up graduation and prepare for IAS exam simultaneously.

If you still have any doubts or queries, please feel free to comment.

Let me know if this answer was helpful to you and all the best for your future!