Can someone tell what is the best reference to prepare for JNCIE-SP exam?
Best way to prepare for the exam is follow the exam topic closely and practice the the JNCIE study guide. There are few topic which are not covered in the book, that you can search from Juniper website and practice them.
i dont think its Enough
What about Junos Sphere to practice my lab scenario??
You can practice almost everything in Junossphere. I'll say it is best and cheapest way to practice.