Welcome! Check out the specific forum for your phone. People in the forums are very helpful around here.
My essential apps are pretty basic: Google Voice, Dropbox, Netflix, Dish Network, Authenticator (you should turn on Google two-step authentication if you haven't already), Evernote. Those are my every day apps. When I get my Note II in a week or two on Verizon, I'll add Google Chrome to that list.