Hypothetically the avatar would be the best for ceramics. Water is a huge component for ceramics when we look at moisture, being able to control the moisture content would bring a whole new level to ceramics.
Earth is obvious, you can easily bend the clay into whatever shape you wish, and being able to manipulate the clay hands free would be incredibly helpful, as your hands easily absorb moisture and cause cracks and fast drying, and would make working with small amounts of clay way easier.
Metal bending would also be incredibly useful, as you could form metal into whatever shape you wish to help trip and shape the clay, and you could even make a wheels
Sandbending could also help with clay dust management, getting it out of clothes, nooks and crannies, and generally protecting your lungs
Earthbending in general would also help sourcing natural clay, helping you get out all the impurities you wish
For air bending, one of the more important aspects pf ceramics is making sure there is no air bubbles that could cause explosions when fired. It would make wedging so much easier and save so much time
Finally fire bending, being obvious, it allows you to fire pieces by hand, and using the other element along with fire you can build a pretty effective kiln (being gas, electric or bending powered)
Water and earth bending be used together would also help with glazing, it can help you mix and distribute the components equally, and apply the glazes as well. You can also add or remove parts of and element as well for desired effects, like adding water for a water color effect, or using air to have and airbrushing effect.
Finally, Clay is a fickle thing, depending on what you need to do you need to use different techniques and philosophies, so this would require one even if the only use one element to employ the philosophies of other elements.
So I am proposing a story where either an avatar in a time of peace gets really into ceramics and masters the elements that way
That or a group of benders establish world peace by teaming up to create the world’s most powerful ceramics studio.
Thank you for coming to my Ted talk