In summary, the best way to find out what kind of bean and roast you enjoy is to buy small amounts and test them. Some people like Italian coffee, while others prefer coffee from the United States. The grind is extremely important, and that's also a matter of personal preference. Brewing method is also important.
By the way, you can reduce the amount of coffee in the basket to vary the strength, if you want. Be sure to relieve the steam pressure (using the frothing wand) before removing the basket. Steam is nasty stuff.