Tricky nowadays. I was able to make a whole Skaven team from the Gutter Runner box (including a 'rat king' as a rat ogre, and adding a couple of spawn pieces for mutations). Wood Elves, the old archer box was pretty good, although you might need to add 2 wardancers. Dwarves might be doable with that Fyreslayer set. Now we have AoS, the models in a single box just aren't right for Old World style BB. Unless you want to use on of those Start Collecting boxes, you'll just have to be creative and judicious with pieces from your bits box.