I've used both Dwarves and Gondor a lot, so here's my advice for playing your Gondor opponent. I hope you find it useful.
First of all, using two-handed weapons is a really good idea against Warriors of Minas Tirith. For a start, it's a point cheaper than a shield, and a shield won't help at all in combat. The +1 to wound doubles your chances of wounding, where as your higher Fight means that the odds of winning the fight aren't too much against you.
For my archers in a Dwarf force, I would normally use a mix of Rangers and Warriors. In your case though, you might as well take the Rangers, and the higher Strength bows on the Warriors will most often not have an effect.
Khazad Guard and Iron Guard are both good, and will really help you break through a Gondorian shieldwall. In fact, if you're not going to use Dwarf Warriors with two-handed weapons these guys are almost essential. And even if you do take the two-handed weapons, they're still nice to have. I personally would take Iron Guard over Khazad Guards, but mostly it just comes down to preference (or you could even take both).
Now for Heroes; Balin is good, and probably underpriced. Taking Durin's Axe for him isn't a bad option, but for that amount of points I'd rather have Gimli. Dain is good at cutting through troops, but not great against other powerful Heroes due to his relatively low Fight (and I'm expecting your opponents, being a beginner and taking Gondor, will have either Aragorn or Boromir). Durin is another good Hero, indeed he's among the most powerful fighters in the game, but he pays for that power with his points cost. Instead of him you could potentially take both Gimli and Balin. On the other hand, Durin, like most uber-Heroes, is pretty fun to play.