Hello Aspirant,

To be an IAS or  IRS officer one has to qualify in the civil services examination conducted by the union public service commission of india (UPSC). This exam is conducted every year and recruits candidates to 25 streams/divisions like IAS, IPS, IFS, IRS etc. This exam is conducted in three steps

1. Preliminary examination
2. Civil services main examination
3. Interview

For preliminary examination there will be two papers.

Paper 1 (2 hours long, 100 questions with 200 marks)

• History
• Polity
• Geography
• General knowledge
• General science
• Current affairs
• Economics

Paper 2 ( 80 questions, 200 marks in 2 hours)

• English proficiency
• Reasoning ability
• Quantitative aptitude/mathematics

Keeping this syllabus in mind I would personally suggest the humanities stream.

You can find further information in the link provided below

https://www.google.com/amp/s/competition.careers360.com/exams/upsc-civil-services-exam/amp

Hope this helps and Good luck