LOL, I was just down in Lumberton last week. There's a big medieval re-enactment down there once a year in March and they have a market full of merchants, some of whom are selling fabric. $5 a yard linen, baby. Ca-ching! My husband and I were racking up. I got 10 yards of a buff linen for underclothes and my husband got some tan and a grayish purple for an 18th century outfit and a new medieval one. Of course, we have to be more picky about our historic fabrics because we can't use prints and I've gotten to where I'll not use polyester unless it's a small amount in a blend. So we're always on the lookout for good linen and wool and silk prices. (Although I snap up cotton material for $1 a yard to use for patterns/drafts; I don't care if it's printed or not.)
My suggestion to the OP--can't remember if she had a JoAnn's or Hancock's--is to wait until patterns go on sale. I almost never buy a pattern for more than $1.99. That way you can afford to get more than one.
Also, how complicated a dress do you want for your daughter? With the help of a book on pattern-drafting, I made mine and my husband's medieval patterns. Some practice is all it takes. I have what they call a sloper--it's a pattern that exactly fits him and me. Cut out and put together it's a cotehardie for us, but with some alterations here and there it can become 300 years' worth of clothing. Children's clothing is almost always more simple to make than adults', especially if you can stay away from zippers (I find buttons much easier to deal with). So, do you feel up to taking a pattern for your girls that you already have and making it into the dress you want? Messing around with patterns is exactly what I buy $1/yd fabric for.