Being a 2nd-year student is too early to start preparing for UPSC CSE. You might tire yourself out and when the actual time comes to outperform, you might not have the energy left to cope. Here are some guidelines that might help you prepare for this exam well in advance.
However, just reading NCERTs will not suffice for the exam. There are some additional standard books that you need to master to prepare well for your UPSC CSE exam.
These books will help you become well-versed in various topics asked in UPSC CSE.
The major prerequisites for preparing for the UPSC CSE exam are NCERTs, the standard books I have mentioned, and The Hindu newspaper. These will help you ace the exam. Additionally, you can work for NGOs to get a sound knowledge of prevailing issues, and practice writing answers and you will be well on your way.