I found this adorable free crochet dress pattern for free on Craftsy.
It's called a Pretty Waves Dress and can be easily adjusted to fit any size. Also, the ideas of making the straps for the dress and possibly making them more narrow or thicker depending on the girl you are making it for. Make it for a little girl in her favorite color.
What type of yarn do you use when making a dress? Most suggest using a worsted weight yarn. Be sure it is a durable yarn that washes well.
Red Heart with Love Yarn - It comes in a variety of colors and is similar to Hobby Lobby's I Love This Yarn. Great for sweaters, hats and clothing items.
Caron Natura One Pound Yarn - While opinions vary on this yarn, I like working with it because of it's easy of use and the large amount of colors.
Lion Brand Pound of Love Yarn - This yarn is wonderful for baby gifts.