Coming directly to answer of the question. After RBI regulation, several cryptocurrency exchanges stopped their operations while other found a way to buy or sell cryptocurrencies and is legit way.

Previously, I was using Unocoin, Zebpay, Koinex, Bitbns. They all are good having instant withdrawals and deposits. But now, Zebpay closed its exchange. Unocoin is good but is more complex while they can do much better in terms of User experience and automation but still a lot to do.

Now, as these exchange stopped directly working with banks. They started P2P trading. P2P is Peer to Peer trading in which, buyer are directly dealing with sellers and exchanges are just for finding and providing right buyer to right seller.
Currently, you can use Koinex, WazirX and Unocoin to sell or purchase any cryptocurrency in India. I think it is safe according to me.