barb is good class and one of the "OP" classes in game but you'll have a tough time against magic classes unless you are vit build, play defensively or more experienced/geared than your Arcane armored enemy.
i personally use 2 sets of accessories(Pdef neck & belt and mdef neck & belt). get all the new NH skills they are awesome.
i think both cultivations are good and i have played both demon and sage r8. so it's really up to you but most 1v1 and mass pk prefer Demon for them crits.
for a guide on builds, Deno/Sensus made a good guide before you might wanna check it out he explains all the basics of the Class and even go in detail on some parts.( he is in my opinion one of ,if not the best barb in server (Aps/Dph)/1v1/mass he is elite so following parts or all of his guide will help you start up greatly)
here is the link ;
http://epicpw.com/guides/how-to-play-a-barb/for levelling what i do is wear HA armor and poleaxe or dual axe and go STR build while sharding vit stones on my armors. i pull as many as i can(half cave) then if without culti or sage = bestial rage>invoke(turtle)>tree of protection>tangling mire> armageddon. one trick is to use Violent Triumph(anti-stun skill) whenever you can't avoid a Magic Mob while pulling so you dont get CC'd.
on demon:
bestial rage>invoke(turtle)>roar>sunder>tangling mire> armageddon = profit
i also found a video levelling guide on forum as well that you may want to check
here:
http://epicpw.com/guides/leveling-a-barbarian-from-1-150!-%28video-guide%29/barb can be fun and i hope you enjoy playing it like i do.