The only approved ways of managing money are:
1. Get a PMS(portfolio management) license from SEBI. You need to have networth of 2crores, pay Rs 10lks registration, and an annual cost of Rs 5lks. Getting a license is not very easy, you need to have experience and qualification. You can't accept lesser than Rs 5lks from each client, and most importantly you can use F&O only for hedging. You can't naked trade F&O.Check this info from SEBI
2. Start a mutual fund, networth requirement of 50 crores, quite tough to get started, but you can have clients putting in even Rs 100. Again F&O only for hedging the portfolio. Check this info from SEBI.
3. Start a hedge fund (AIF - alternate investment fund), minimum size of the fund should be Rs 20 crores and minimum individual investment of Rs 1 crore. Check this from SEBI.
4. The only real way for someone like you to do this would be by registering with SEBI as investment advisor and advise your clients when to buy/sell. In this case you will not be able to execute the trades on behalf of your clients. Networth requirement of Rs 1lks and yearly fees of Rs 10,000. Check this link on SEBI.
The above are the only 4 ways in which you can directly/indirectly manage other people's money in India, and which is approved by SEBI/NSE/BSE.