I saw the Hobbit The desolation of Smaug yesterday and that has renewed my interest in the game, I didn't get very far with it last time.
I want to start playing a Dwarf army, either old or new or even a mix of both!
I have at the moment:

old Balin
Dain
Gimli
4 dwarf captains
1 dwarf king
4 dwarf warriors
14 dwarf rangers with 2 handed weapons
12 dwarf rangers with no options
13 dwarf rangers with bows
and 2 standard bearers

I don't know what I should get next to fill out the ranks a bit, I was thinking of a new hero and warriors of Erebor, but I don't know what else, it looks like it might lack power as it is just squishy rangers.

any help is appreciated

Personally I'd recommend picking up some Khazad Guard and Dwalin and some Erebor Dwarves, Erebor Dwarves can bring spears and Khazad are probably the most well rounded dwarf troops in the game. And of Course Dwalin is an absoulte beast, hardest hitting Dwarf Hero in the game

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I agree, i like to play dwarves, i chose warriors of erebor as they have spears. I also did khazad guard as they have high defence and are cheap. Iron guard i find are also good as they have two attacks. And although it is a bit irregular, i ally in elves as they are the best with bows and also have good fight values.

So Dwalin Erebor Dwarves and Khazad guard, sounds good already
would giant eagles or ents be any good?

Yes they would. Almost any time you can bring monsters it's good. For the Dwarves the Eagles would be best as Dwarves have no cavalry so their speed helps.

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Commission Painting @FB http://www.facebook.com/squyrepainting
Commission Customers include:
GBHL Youtube Channel
MiniWargaming