Hello Clownhammer, and welcome aboard.
Almost everything has been said.
I can garantee you that this game IS fun! I almost exclusively play at it since now 2 years, and exclusively in SP, and I had, have a LOT of fun!
All advices are good: try small games with victory points to handle basic game mechanisms.
Then, try some nations which you think fit you gamestyle.
Read A LOT on this forum! Especially the strategy index, and try that is explained.
Try every spells that inspire you and see what happen.
Whatch the battles, and you will learn a lot. Adjust your army placement and your commanders scripts and look at the results.
If you want to really go deep, you have to learn handling magic, and for that play some games in EA with magic site frequency set at the max to experiment a lot.
For nations, EA Abysia is one of my starting ones, along with EA T'ien Ch'i and EA Vanheim a bit, but I don't recommend the last for beginners. Arcocephale is also a good choice.
MA Machaka is versatile in magic, but a bit tricky to handle at first.
I would not advice trying SC or thugs in the beginning, because I think that it requires some game comprehension and some magic items experiment first, but it's your choice, and as parcelt said, it may fit you. Try it.
Well, that's a lot to try!
But as JimMorrison said, the real treasury is the content of the game, and I must admit that, after two years of playing, I only discovered probably less than 10 or 15 % at most.
So, you have many long years before you
I can say anything about MP, but I must correct you: it is NOT all about MP with Dom3! Believe me!
See you around on the forum.