If you often use mobile for doing bitcoin stuff then go for zebpay .their service is good and reliable.for desktop you can try coinsecure or unocoin,its your wish which one u want to use as they both are good.unocoin often give signup bonus also so you can try it.
All three have good service, while each do have their own unique features (Coinsecure with automated trading, Zebpay with vouchers, recharge, etc and Unocoin with VAS and SIP option)
For cheapest rate, always use coinsecure.in/ they show the real rate, even if their competitor offers a better selling/buying price.