Jim Cramer breaks down what earnings reports to watch in the week ahead. Cramer says he remains a fan of Costco and advises those who trade on the headline numbers to wait and see the full text of Costco's report next week. He says the stock has been resting for a while and it may be time for another leg. Now that its partnership with American Express has ended, Cramer predicts Costco's gross margins will go higher because they got rid of that deal. When it comes to Kroger, Cramer says it looks good but he stresses to be aware that competitor Whole Foods may be the horse to bet on for 2015. He reveals that he'll also be watching Best Buy to see whether lower gasoline prices will finally be prompting consumers to spend extra disposable cash there.