Yes, you certainly can wear tights with a knitted dress and this is a standard way to make the dress look even better and to keep you warm. It's important to match or contrast the color of the tights with the dress so it doesn't clash or appear overwhelming and be careful with patterned tights if the knitted dress has its own bold pattern. Other options include knee-high socks, leggings, jeggings, exercise/yoga pants and even skinny jeans under a knitted dress.