When I taught ceramics we bought local clay (well, not "local" but from New Jersey, the state where I taught), and we got a white without grog for throwing and a red with grog for handbuilding. Tools, and boards were separated according to color clays, and 1/2 the class would be handbuilding while the other half threw on the wheel (then they switched after a certain time).
You can marbelize the two clays together, but make sure you keep the scraps, water, tools etc, distinct from the white and red clay bodies. Marbelizing is when you wedge the two bodies together, make the piece, either handbulding or wheel thrown and then sand off the outside thin layer when it is bone dry, then fire it. You can just throw on a transparent glaze and leave it at that.
Both clay bodies fired at 05-06 for bisque and could go up to stoneware if we wanted and they were compatible with Amaco glazes.