Last summer as I was going through my daughter's clothes I realized something. I had several items from the year before that were a little big on her but still fit the following year. Then I had a huge DUH moment. Why not buy most of her clothes a little big so that she can reuse them the next year?
Now, this doesn't work for everything, but for things like pajamas, dresses, etc. I always buy one or two sizes big. It has saved me a ton of money as I don't have to purchase a new wardrobe for her every year.