I think a discussion of revenue options would be a great thread sometime in here, but basically speaking More Players = More Revenue. Thus SEO is, like we've said, extremely important and highly rewarding. Tons of it can be done for free - writing blogs, contacting blog writers, engaging the community here and in other forums, social networking, etc.
PvP will be one of those features that will draw in the crowds and is most affected by how many players are playing. For it to be optimal players have to be willing and able to engage in it often, meaning they can't be afraid to do it, or bored of a tedium of it, or unable to find opponents, or other troubles mentioned in other threads. Better PvP will translate into more subscribers very fast, and with good Crown-selling ideas such as in Ailric's other post here about Improving PvP
, there will be many more players very willing to happily pay to play the game more without turning it Pay-To-Win.