Too soft a seat can put you right to sleep. Too hard can promote pain. The clothes you wear for meditation should be loose and soft. If you are wearing a belt, loosen it. Don't wear tight pants or pants made of thick material.
Long skirts are a good choice for women.
Loose pants made of thin or elastic material are fine for anybody. Soft, flowing robes are the traditional garb in Asia and they come in an enormous variety of styles such as sarongs and kimonos. Take your shoes off and if your stockings are thick and binding, take them off, too. When you are sitting on the floor in the traditional Asian manner, you need a cushion to elevate your spine. Choose one that is relatively firm and at least three inches thick when compressed.