To get the desired books for semester one at Delhi University, you must make a list of books that are required for that specific semester.
You can get the required books from the library but sometimes those books are not available in the library then it is a better option to get the books from the market as they can be reused always and there will be no need to return them within time as per the library rules.
Now talking about where to buy the books from, you can buy them from mypustak.com and they deliver the books to your doorstep with no extra charges and only minimum shipping.