I looked into it a few years ago, yes, you do need to buy the bran stuff every time. I had access to outside composting for free, so it wasn't a good deal for us. A quick internet search will find you instructions on how to make the bran at home, which would bring down the cost and might make it worthwhile, but free is better, IMHO.
Worm farms seem cool, but I've heard tales of the worms wanting to explore the house, and also of people having issues with fruit flies. All in all, a small, lidded, bucket next to the back door emptied regularly into an outside compost bin works best for us. I use a 10 liter food grade storage tupperware style bin with a carrying handle, which is plenty big enough for us. (2 people, emptied weekly in the winter, because it's cold and dark, and daily in the summer)