Lawyer

Law is the most diverse field in the world for a simple reason that everything in our world is regulated through rules. Hence, it's suitable for anyone and requires only one skill that is reading.
Coming to your question of scope first. As far as conventional practice of law is concerned you can do it anytime you want. That requires sincerety and continuous hardwork and the growth is exponential with experience gained. The corporate sector has opened many job opportunities offering good pay packages in lakhs. There are also law firms wherein you have to work in a firm full of lawyers, the money is good there too. Apart from this you can pursue, LLM and PhD and become a professor. Judiciary also recruits law graduates directly for the post of Civil Judge /Magistrate which are at par with IAS / IPS. If one can clear the judicial service exams in late 20s there is no one stopping him but himself from being a high court justice. As a lawyer one is free to do anything else he likes. I have seen lawyers who pursue their hobbies as they are their own bosses and manage their own finances/cases accordingly. You can write books and become a publisher. You can become a Govt Counsel or Advisor or Attorney and the growth here is also endless.
Now the 2nd part which is preparation. Their are coaching centres across our country but in my experience UILS Connought Place Delhi happens to provide best coverage for CLAT preparation. Getting a good college through clat is like getting a power play in 20-20 as You have many advantages of infrastructure , fraternity and Faculty. Getting into the top 5 National Law Schools will take you to another stratosphere itself. CLAT requires good command over English (Wren & Martin + Word Power is sufficient ), General Studies & Current Affairs (Lucent is sufficient ), Legal Aptitude & LEGAL Reasoning (Here is where coaching is useful, but if u can't afford then go for Universals Guide for LLB Entrance Exam) , Mathematics (Elementary level no big deal)
hope this is helpful .