Feel overwhelmed when you want to buy skin moisturizer for your dry skin? That’s no surprise, as there are dozens to choose from at the drugstore and hundreds more at high-end cosmetics and department stores — creams, lotions, ointments, some with sunscreen, others with an exfoliant. Choices range from the basic $1.50 jar of petroleum jelly to a $500 five-ounce tub of designer skin moisturizer. And all the options in between can make your head spin.