Re: MF Barbarian
Polearms are too slow. A sorc could get by with an Isted Occy, Isted Shako, Isted Skulders Ire, and the rest of her gear be MF and if the build is good still have a decent chance of killing Hell Meph or Pindleskin. A Barb needs things like LL, A high damage weapon, AR, and usually DR to even survive Hell and actually kill things. That doesn't leave as much room for gear.
Some good options are IK help with 2 perf Topes + IK boots. None of the other IK items add MF but they do add other useful stats for survival.
If you can get your hands on Tal Rasha's Guardianship using it with the belt and helm gives you 163-172% MF while adding some nice stats. (The armor alone is amazing)
Harlequin Crest can help a barb almost as much as a sorc and can give you 74% MF
Skullder's Ire upped to elite has great MF and the +1 to skills but not much else.
Goldwrap (upped at least once for 4 potion slots) has the 30% MF and the 10% ias can help you reach a break point.
As for builds there are many great guides
here. I would go for one of the cookie cutter builds such as
Halciet's Concentrate guide or a WW build which the link to is broken but is basicly
20 WW
20 BO
20 Weapon Mastery (Swords are a common choice)
20 Shout
and at least 1 point in Berserk, Find Item, and Natural Resistance, and Increased Speed (You'll be doing a lot of running). Don't be afraid to put a couple of extra points in Natural Resistance if you are planning to sacrifice survival gear for MF gear.
Then just get the best gear you can for surviving and beating hell. Once you reach the point where you are Surviving Hell and killing fairly quickly you can slowly switch out regular gear for MF until you find a balance you are happy with.
I hope that helps.