Hello Prashant,

It is difficult but definately possible   to prepare for ESE mains without any coaching.

Things you need to do-

1.Go through the syllabus-you should have clear idea about the syllabus,start from bulkier mark subjects.

2.Get the standard books

3.solve past year questions-This is the best way to get idea about what you don't know,what do 

you want to need to know,work on your weaker points.

4.practise-practise alot more and more questions,practise past 15 year papers.

5.join a online test series- when your 75% syllabus get completed start giving online test series.

6.focus on speed,accuracy and presentation of your answers.

7.Make  clear notes and revise all the notes whatever you have. 

hope this helps.

Good Luck.