Coinbase is by far the most popular bitcoin exchange for gamblers based in the United States. While Coinbase officially don't allow their customer to purchase cryptocurrency for the purposes of online gambling, poker players and sports bettors in the U.S. have figured out that they just need to use a middleman wallet like BreadWallet or GreedAddress to act as a buffer between Coinbase and their gambling site of choice. How Coinbase have made purchasing bitcoin even easier for anyone that has a United States bank account. In the past, Coinbase users had a wait a number of days before they could make a purchase after they had transferred money from their bank accounts. This rule is now gone, allowing Coinbase users to instantly purchase up to $25,000 worth of bitcoin, litecoin and ethereum. If you are eligible for instant bank purchases, you will receive an email from Coinbase as soon as the feature is available.