How many grams of sugar do I need per day?

You don't need any sugar. You're body will break down carbs to create the glucose you need so there is no nutritional requirement specifically for sugar. Sugars are carbs. What you should be concerned with are your macronutrient ratios such as 55/25/20 (%calories from carbs/fat/protein). Keep your caloric consumption where it needs to be, mind the macronutrient ratios, and make sure you're eating a varied diet of quality wholesome foods and you don't need to be concerned about anything else.