Well for Spain I opted for a cavalry army since their infantry is crap until you get some fedual foot knights.Hire Mercenary spearmen when you take on the Portugese and the Moors as you can't recoup all the cash by sacking rebel towns in Spain.

My army consists of about 8 Jinetes which pepper the enemy with their javelins until they whittled down to nothing more than a few bloodied men wetting their armour. Throw in the general and some mailed knights and you have yourselves an army.

I then invaded Pamploma and slayed their general, sacking it to get some cash. Then the Pope told me I was naughty and should stay away from them. Which I did. For a while.