I think the best class to buy (if you just play in the good team like me) is the Royal Guard, because you can use it on 3 different maps: Black Gate (a good map to farm points), Edoras and Helm's Deep (a very popular map), it's not weak (i mean, you have a gold chestplate with freakin Protection III!) and it "only" costs 3500 points.
BUT, if you want to be a AWESOME Dwarf, buy Hammerer (4500 points, Maps: Moria <3 (Gold), iron helmet, chestplate, boots, golden leggings, diamond axe with sharp I and knockback I, resistance and slowness), Dale Swordmaster (3000 points, Maps: Erebor <3, iron helmet, leggings, chainmail shoes, diamond chestplate and sword)
or Dwarven Axethrower (Maps: Erebor <3, i dont know more
)