Do keyword searches for the various nations that you try. I am pretty sure every race has some sort of discussion thread.
There are numerous docs that have been made by fans, after you play through a couple games I would take a look at them as they are great resources but will mean nothing unless you have some sort of grasp on the general concepts.
Also, try Ulm with a rainbow mage (Rainbow means a mage with multiple paths, these are excellent at site searching). I still think they are the best for illustrating the basic concepts of the game. They also make for great crafters, which will give you insite on the magic item creation system.
Once you have a handle on that, move to a race with a bless strategy. Ulm doesn't have any sacred troops. If you have a pretender with atleast 4 picks in any path of magic, you can pass on special abilites to your sacred troops. At certain points, you get certain abilities. For instance Fire 9 (very popular) gives your sacred troops flaming weapons (+8AP dmg). Fire 8 however would only get you +4 attack.
Also the Dominions I guides are still semi-relavent and are a good read, and actually explain the basic mechanics pretty well.
The forum is a awesome resource, and you can go back multiple years and pull up information. This has also been one of the most helpful communties I have ever been a part of.
The Dom II Library
http://www.freewebs.com/dominions2/ is a great resource, and also has links to other sites (dominions-x..has the correct link here, unlike the illwinter site). The Illwinter site also has some good resources and has mod links as well.