Usually you use only one layer of batting. What exact brand and type of batting do you have?
You may be thinking you want the "comforter" look in a quilt. This is a modern look that came about because commercially made comforters use high loft polyester batting. Using this high loft batting at home makes machine quilting harder.
Traditional antique quilts used thin cotton batting that shrinks a little in the wash, creating that distinctive soft, crinkled look.
There are many different kinds of battings in-between those two looks, too. Some battings require quilting no more than 2 inches apart, while other types can allow quilting lines as far apart as 8 or 10 inches.
You can layer 2 battings in a quilt, but this is probably not a good idea for a beginner, as it will make either machine or hand quilting more difficult.