You can go with 2, or take it to 5, its a matter of what your comfortable with, your budget, your computers capabilities etc. The fewer characters the easier it is, especially if they are the same class. Decide what you want to do with your crew, figure out if you have the resources to do it in terms of money and your system and then go from there. For example personally I'd like to 5 box, but my system can't support it and a new systems out of the question, so I'm limited to 3.