Jim, you are giving people little info to go on to help you with your "must-needs". What are your specific wants? Games (what kind), Productivity, Sports, what?
I always peruse the Top Paid (in your case, Top Free) apps in every part of the App Store. That usually tells me what is popular.
E.G.:
App Store --> Games --> Card --> (Right-hand corner) Top Free --> 1-100 free apps.