First, I just want to say, whether you go to a coaching institute or are preparing from home, self-study is a necessity.
Joining a Coaching institute for MPPSC
Two types of students are involved in MPPSC coaching in Indore: - First, those who do not have basic clear and second, those who cannot study at home and need pressure to start studies.
So, if you are also one of them then you should join any coaching institute for MPPSC.
The gain or Advantage
• Coaching institutes help you to study regularly.
• Some take weekly or monthly exams, so revision is going on simultaneously.
• Teachers are available to clear your doubts.
• They tell you what is required and what is not for the exam.
Harm or Disadvantage
• They teach according to their own schedule, which may not suit you.
• You may be confused whether you should study for their daily/monthly tests, revise what is happening in the class or study the topics in which you are weak. Which can lead to backlog.
• Sometimes they just want to complete the syllabus and don't want to teach properly.
• You may be disappointed to see so much competition.
• Sometimes the schedule becomes so hectic that students do not get time to study on their own or to solve questions.
Prepare From Home or Self Study for MPPSC

Advantage of self-study
• You can study as per your requirement.
• You can also take some private tutoring which will help you clear your doubts and keep you on your toes. Plus, they won't need much time just for 1 or 2 hours.
• Study material and mppsc notes from Sharma Academy, MPPSC Coaching, Drishti IAS, or other institutes is easily available, so you don't have to worry about it.

Disadvantage of self-study
• You may feel that you are trapped in your home.
• You cannot study regularly.
• You can get distracted and waste your time.

So, if your basics are somewhat clear and you think, you can do self-study and will not procrastinate then self-study is best for you.
Note: If you are preparing from home then you must join a test series. And try to solve mppsc previous year question papers as much as you can.
In the end, it all depends on you. We can't tell you which one is best for you and not because we don't know how you work.