Start Collecting OBR should be the Liege-Kavalos/Zandtos kit, a set of Kavalos, and then Mortek Guard.
Start Collecting Gutbusters should be a partial repackage of Feast of Bones, with Tyrant, Ironblaster/Scrap Launcher, Leadbelchers, and Gluttons.
Start Collecting Bonesplitterz should be a Savage Big Boss, Wurrgog, Savage Orruks set, and Savage Boarboys set.