For teaching—smart casual: men—slacks or jeans with shirt or polo, women—slacks or skirt with blouse or top. You need one good outfit for rare special occasions.
Wear comfortable shoes and clothes that breathe in the heat—natural fibers.
Even though this is Guangdong, you may need long underwear in the winter as it is as cold inside as it is outside. The classroom windows are usually open in winter. You will need a warm coat and gloves if your hands are sensitive. The key is to wear layers and keep yourself warm with hot liquids.
Hot and humid in the summer, cool and sometimes damp in the winter. This is the Tropic of Cancer.
As at my home university you can probably wear what you want for teaching but smart dress is appreciated. I like to wear a shirt and tie for formal lectures, but this is definitely not expected.