Definitely focus on revenue. That way you work towards building a profitable business from day one. If you focus on 'money later' you are in effect first building a user base and then trying to monetise it. Just because you succeed at the first stage does not mean the second will be a breeze.

Also, keep in mind that a startup is really an experiment. Every day you should be learning something new and tweaking your business accordingly. By focussing on revenue you start learning how to make money from the beginning. If your initial focus is on a wide userbase, then you learn nothing about the money-making side which is likely to be very different from just getting users.