Honestly I pretty much use whatever I can scrape together. I like to win battles strategically, by utilizing superior mobility and force distribution to concentrate my strength where the opponent is weak. My main weapon is my florins.

Its a rare event when I'm attacking from fewer than three different provinces. As a result I can't build a 'perfect' army. So I heavily utilize what I like to call 'fire-and-forget' troops. Highlanders, Gallowglass, Militia, Light Cavalry, any Mercenary. They die fast, but achieve a KtD ratio of greater than 1/1 while coming in nicely sized units. Add in a couple Feudal Sergeants to provide a line for my fire-and-forgets to flank off of and a core of a couple/few ranged units and always, always one heavy cav.

The basic plan is to be willing to sacrifice as many men as possible to achieve victory. Two units of mercenary Italian Light Infantry can hold off five times their number long enough for you to exploit the numerical superiority of all other forces on the field to crush the opponent. Sure, those two Italian Lights will rout and be annihilated, but by that time the enemy has a few hundred men and you've still got half a stack.

Now unfortunately this doesn't work in the desert. You see the Muslims love routing and regrouping, and have hugely massive numbers. In addition, operating from an ocean away I can concentrate force on any single province to attack it, but I can't get off the coast using my standard tactics. So I make a super-stack. My best General always heads my Middle East task force, which consists entirely of national troops. Can't trust mercenaries when reinforcements will be unavailable for the 4 years it takes to build a port. No bows, only lots of arbalests, two units of Hobilars or equivalent light cav, lots of the best spear available which is hopefully Chivalric Sergeants. Also, one or two units of the best knights available, dismounted. Find the biggest hill and set up the world's staunchest static defense, and do not, ever, ever, ever chase down the enemy. Let the rout, reform, attack, rout without doing anything, reform, etc. Their 40+ units aren't a big deal when only a few reinforcements manage to trickle in before the defenders win by time. The cavalry and foot knights are there to render the troops impotent, by killing the enemy commander. Always, always ALWAYS kill the Muslim prince who's leading the huge attack. The morale penalty guarantees that their forces will waste twenty minutes or more rallying, charging and routing before they touch you.