Some beginner questions

[how786]

Thanks for all the excellent input. Altho I'm only at turn 27 of my very first game, I can appreciate the great depth and complexity of this game. Wow! It presents a daunting task for a newbie like myself.
I'll give the rainbow mage a try.
Could you define 'choke points'?
The tricky thing about Forts (are you also referring to them as castles?) is their ability to drain resources from adjacent provinces, which, if not well thought out, can create problems. This area seems 'above my head' right now. The choice of WHERE to place them.
Last night, I had a fort in a nice province close to my capitol. I kept trying to recruit a rather cheap commander to man the defense force there but it never would appear as acquired even tho it appeared I had both the gold and resources.
Also, it seems that I always have unspent resources after each turn. I'm wondering if there is some way to use these well other than buying troops.
Could one of you elaborate as to how gems are used to raise mage skills? I've not figured that out. Is it a temporary elevation or permanent?
Also, how does I fast forward or speed up combat?
I appreciate the heads up re:PD. I did not know about it. Sounds very useful.
Thanks for all the help! Keep it coming. please. I'm soaking it all in.
How786