I am a huge discount shopper and can't go into a store with out a quick run through the clearance section. I found this size 18 skirt at Justice for $3.00. My daughter wears a 6.
I unpicked a 2 inch section of the waistband and put a button hole the width of the elastic in the inside waistband layer. Then I pulled the elastic out and sewed it together so it would fit. Thread the doubled over elastic through the button hole. Re-sew the waistband.
Now when she gets bigger, I can unpick the elastic and re-sew it without opening up the waistband again.
I like the option of making it bigger bc I only have 1 girl!