which course in DU should I Pursue in order to have a future in UPSC-CSE?

Hello,

First of all there is no such restriction in term of belonging to specific stream for UPSC, one needs to complete graduation in any discipline from a recognized university, now you haven't mentioned your combination of subjects at 10+2 level, there are two ways here, choose humanities like BA(Hons) in Political Science, History,Geography, Economics, Public Administration etc if you're wholly and solely focused on UPSC Civil Service only, if you're not if you belong to any other stream like Science or Commerce, you can pursue this discipline as well, there have been many people belonging to engineering, CA, medical field who after graduation have earned few years of experience in their relative field and then applied for UPSC, if you are not sure go for this option. UPSC doesn't discriminate among aspirants hence people from all backgrounds are allowed and it's good to have a back up plan as well, if you see toppers of this year or even previous years they come from diverse backgrounds such as medical, engineering, CA, arts, etc. Yes, we may say that perhaps humanities students are already acquainted with the syllabus portion in a way other stream students aren't, but that doesn't matter, if that was the only case, then other streams students wouldn't even have qualified for this. So, it's entirely up to you whether you want to have a back up plan or don't, majority have but then it's an individual decision, you can start your upsc preparation even in college with little efforts like learning the humongous UPSC Syllabus by heart which will enable you to know what to read and what to skip in your preparation process,
reading The Hindu on a daily basis, going through NCERTs book which will build your foundation etc.

Hi

You can choose any subject or course  of your choice based on your interest for your graduation in DU like Bsc, Bcom, BA etc

This is because,

to be eligible for UPSC  examination there is no compulsion to be a graduate in a particular subject, all you need to be eligible is that you should be a graduate in any discipline

So you can choose any stream of your interest, but yes if you choose BA or Arts

then

choosing Arts or the humanities can be really helpful for your UPSC  examination, this is because in Arts you will be learning subjects like history , polity etc which are a part of the UPSC syllabus so it will help you in your upsc examination.

Thankyou