Hello there Canada!

As far as sculpting figures etc, I've only ever used Milliput putty and it's lovely stuff to work with (once you've washed your hands clean after mixing the darned stuff)! When I started all those decades ago you could only get the original pale green version and that was perfectly good for most things. The newer white 'Superfine' is better for adding fine textures etc (as the name suggests) but is more expensive. I've had some less than complimentary comments about the newest black one though - doesn't seem to stick to anything except itself apparently!
But for general sculpting, the standard, silver-grey and superfine are excellent, even the terracotta is good too (makes great red bricks for dioramas). The main thing is to ensure it is fully mixed together or you might get parts which don't go completely hard as it cures and for sculpting body parts there's nothing better than a finger dipped in water to smooth the surface down.
Best of luck and show us how you get on!

Robin.