What pellets do I need for my airsoft gun?

I just bought a mp001 airsoft sniper rifle because I heard it was a good gun and I dont have $200 in my pocket. but I was wanting to know what size bbs I need for most accuracy,range,and velocity I thought the .20g bbs were good but I didnt know. and also were is a good place to get a good quality scope and bipod for under $35.