I'm not too sure if all the new brands of colour and clay shapers exactly match (the ones in that amazon link seem to have longer heads than the original Royal Sovereigns), but assuming they're close enough...
Size 0 are good for miniature sculpting. The heads are about 5-7mm long, and 3.5mm wide at the ferrule. Size 2 (7-11mm long, 5mm wide at the ferrule) are also useful for any slightly larger surfaces or sculpts, and then obviously, size 6 for the next step up. But I think size 0 is enough to go on for starters.
I have to say that I think even the black, extra-firm shapers are still a bit too flexible for most work, pushing congealing
GS around, compared to a metal or wooden tool. Ditto for the fine points and edges that might be needed for tiny miniature details, being as they are, pieces of rubber on a stick.

I tend to use them more for final smoothing and some subtle surface details, and for that I mostly use the round cup and taper point. But that's my experience, and I say play around with them to see what shapes you like and for what jobs. Especially when you get the whole wallet for that price.