promotion failure

x, y, z, w-categories there. x Over $ 50 for a product within the category of shopping, I would like to gift items. $ 50 dollars worth of products in the basket while the other types of promotion comes into play again. But I would like to have this promotion for products that only the x category. Despite all the trials, the values ​​I had no success. If you share that idea on this issue urgently