Let the game guide you for the first few steps. Yes, a mine is important. Start with wood and ore (stone), or gold. These are the basic building materials. Higher level structures need rare resources such as mercury, gems, etc. You want to build a tavern in your town. The game should show you this. You can hire up to 3 heroes...and combine their troops if you want. Send me an in-game email. With Kam, that makes 6, ranked #4 now.
We're tied for #1 Alliance out of 83 total, already. I'll post a screenshot, because you never know how these things will last in online games.
Looks like the Human faction is the best for noobies. The Angel/Archangel units seem to have the best payoff. I still say go with what looks fun. There's more to a strategy game than picking the best. It's being the best with what you have.