It is pretty easy, yes. Just go over to the multiplayer forum on here or
here and look for any games that might be starting. If there aren't any looking for players, you can always start your own game and it shouldn't be too hard to fill up. It's pretty easy to start up a game, but if you're not quite sure you're up to it you can usually find someone willing to set games up for you.
As far as complexity goes, the AI really isn't capable of providing that. It pretty much only has one strategy, and what works against it isn't the same as what works against humans. You can still use it as a training tool though to figure out how the game works. There's a huge level of complexity and decision making in this game, starting from your choice of pretender. Your pretender choice can significantly effect how your nation looks later in the game and what it's capable of doing. What magic paths you research at what point in the game also is a pretty big thing, and something you need to think hard about. I think the more you play, the more complex you'll understand the game to be
Especially in multiplayer where diplomacy becomes a significant matter to consider.