Cosplay for less by alison-boyd-rasmussen featuring a v neck tee
You can cosplay with your BJD for less when you use Nine9Style items. I've been able to locate some inexpensive items on Polyvore for your enjoyment, though you may need to plan ahead a little (that white pleated skirt may take some time to arrive). You may also be able to locate a few of these items for less on eBay.
The nice thing about a casual cosplay look is that the pieces will be able to function for everyday use in your wardrobe, without being too costume-y. Have fun at your next convention!