I'd say your top priorities should be (in this order): 1. Keeping your existing players as long as possible (Retention) 2. Making money (Monetization) 3. Getting new users in the door (User Acquisition)
It's a tough environment right now, and you can easily spend all your profits on marketing--so you have to make sure you're maximizing the Lifetime Value (LTV) of every install.
As a product manager with experience working on games for Zynga, Disney, and a few small gaming companies, I can tell you that free to play games are more like an on-going service than a make-it-and-ship-it console game.
Successful game developers generally follow the same pattern: 1. Collect data to see what players like / don't like 2. Analyze the data to decide what to do next 3. Implement a change / new feature 4. See if it worked 5. Repeat
Data-driven decision making is key to making sure you're investing your engineering resources for the highest return.
I'd be happy to talk in more detail.