Step one, find some elastic. I have lots (since I make tutus for my ballerina bowholders,too), but the very first one I made using some elastic out of some old clothes waistband. Measure your girl's waist, add maybe a half inch for overlap (to sew together). You can handstitch it really quickly, no machine needed.
Next comes the tulle. You can purchase the 6" kind on rolls in craft stores. Get about 50 yards (you may not need this much, but the more tulle, the fuller and fluffier the tutu!). The rolls are usually 25 yards, so 2 of those (unless you want more than 1 or 2 colors in your tutu, obviously!). Those usually cost about $2 apiece.
Figure out how long you want the tutu to be. There are so many lengths, each with a different look. Cut the tulle double that length. The amount you use will vary.
Fold each piece of tulle in half, hold against the elastic and wrap it around, pulling it through the loop at the top.
Repeat with each piece until you get the desired fullness. Experiment; you can always untie if you don't like the way it looks! If you want, take some of your extra tulle (if you have any, and wind it around the waistband to hide the individual tulle tie ons(but it doesn't look bad as it is!). You can add embellishments like gems or ribbons, too.
Put it on your little ballerina, and watch her dance and prance and have fun!
Now how easy was that?!! Great gift for a little girl, especially if you're on a tight budget. If you still don't want to do it yourself, you can find more affordable tutus- I wouldn't suggest spending more than $15 on one, though. The other thing with a DIY tutu, it'll grow with your child for a while- just add more tulle!