(These notes are for NORMAL, not HARDCORE mode. Not yet. And on Normal difficulty.)
Okay -- you've gotten your character up to level 4 or so, you've picked your first skills, and you've even got some gear. You're on your way to defeating the Big Bad Boss at the end of the game -- and unlocking the increasingly harder Nightmare, Hell, and Inferno difficulties.
Now -- let me add a note up front, here -- this is YOUR game. I have some tactics that I use, but this should not be considered "set in stone." I use "whirlwind" a lot, but you might prefer to have Seismic Slam or Hammer of the Ancients (both of which cost less energy) on your right mouse button. I prefer to play with a shield but you might like the two-handed weapon best.
It's your game. Set the game up however you like it. Experiment with things -- that's what makes games fun! If you have a group that you play with, then talk to them and ask them how they'd like you geared (the strategy may be for you to run in and take lots of damage while everyone stands at the edges and picks the little guys off and someone heals you, for instance.) But if you're playing it solo, like I do, just make characters and have fun!
So... Barbarians...