Should I Develop an App for iOS or Android first?

Do your homework. Find out the user-base quantities of both in India and then base your decision on that and the potential profits from each. If you plan on developing internationally (as many in the Google Play store seem to do), then you need to factor that in -- Do you have a support structure to translate your app into other languages? This forum is not really the best to ask your question. Try both Google and Apple's tech forums.

 

It also depends on your level of technical ability and familiarity with mobile development. iOS and Android present very different challenges. The time it takes to create an Android app is typically shorter. However unlike iOS once you get your app working on one device you can't be reasonably certain it'll work without a hitch on other devices. With iOS if it works on one iPhone it'll work on all of them with the same version of iOS. The list goes on and on.

As @KevinJames said — as an app developer your goal should be to get your app to as many users as possible. So figure out which of these two targets will let you achieve that in the shortest time possible and start in that direction.

 

Android and iOS is totally different system, you may need to learn much!