What spells would be needed to move a clay sculpture in a lifelike way, but not permanently or like a golem? I figured that a rego Terran spell would be needed, but aside from that I’m stumped!

Under the existing Rego Terram guidelines, I would simply use the Base 3 Guideline "Control or move dirt in a very unnatural fashion", adjusted with additional magnitudes for the type of material you are trying to animate:

+0 (dirt, sand, mud, or clay)
+1 (stone or glass)
+2 (gemstones)

So, as long as you have a clay statue ready for use, animating it shouldn't be too difficult. Alternatively you could also borrow the guideline from Herbam for animating plants or plant-based materials (Base 10).