Can I start my baby on rice cereal?

My baby is 15 weeks old, and will be 16 weeks on Thursday. She is always hungry, She will eat like 6 oz every 2.5 hrs. Everyone keeps telling me she is a big baby, no one believes me when I tell them her age. I am not sure how much she weighs, but at 12 weeks old she was 14 pounds. She has gained since then though, I am guessing she is between 16-17 pounds now. She never seems satisfied, and she also has reflux, so she projectile vomits a small amount probably about 20 times a day. She sleeps like 11 hours at night, so I am not worried about her sleeping at night. Should I start her on it? If so should I feed it to her in a bottle, or with a spoon? How much should I give her, and what consistency? Thanks!