Lots good input from the rest of these guys, so I'll just add a few small things. The 5 difficulties are balanced such that you won't need to worry about the game being too daunting, imo. If you just wanna focus on learning mission mechanics without being overwhelmed by bugs, you can simply play at a lower difficulty. There's nothing lost by doing so, just that experience and gold gain scale based on it. No content lost.

Like many games, there are tricks you can learn (a lot of animation cancels). The game isn't balanced around them, though, but they're also mechanically simple to execute if you do choose to seek them out later on.