Wear what makes you feel comfortable.
However it is important that we , as teachers, can see what your body is doing so allowing for corrections.
You also need to be able to move freely. Breathable fabric is the best solution.

 Socks are fine at first , then maybe later you can purchase some dance shoes.
No, I always give adjustments as I work with different levels.
Then I can always give a one to one class to explain the basics with more details.
Please bring a water bottle and if you prefer to use your own mat for stretching.