I'll do this in my quick story method... Playing as Spain in Normal difficulty.
Title: Spain, Eternally Second
The Early Years:
Ah, welcome to spain... city of light, city of love... no wait, that's Paris... my bloody allies who seem hell bent on world conquest. It looked like a good idea on paper! Spain begins with a crap army, crappy city developments, crappy technology, but great trading ability. Also to our advantage is the fact nobody really WANTS to go to spain, having no tactical signifiance whatsoever.
I begin with a no-brainer opening move: Take Gibralter (Worth 3 glory a turn!). Along with the French Fleet, our spanish ships are able to drive Admiral Nelson into the Mediterainian. Strangely enough this would come back to haunt me later, as he would be there for the rest of the game. I now lay siege to Gibralter, blockading the port, with my entire army.
Gibralter falls a while later. In addition to the collapse of Gibralter, France has now moved and is sacking Austria. My army turns it's attention to Portugal, which is worth 1 glory a turn, and will be very useful in building more units. WIth much tact and grace I maange to take Portugal without damaging the Portugeese army too much. This means I get to take control of Portugal's army as well, and it is pretty much unharmed. Portgual becomes my Protectorate.
Hey, im doing pretty well! By the time I am finished with Portugal Austria has surrendered. I am well into second place, France leading since they were battling so much while I did little but lay siege. The Kingdom of Naples has levied its first army... things are looking up.
The Middle Years: AKA: Spain Screws Up.
With my Austrian Surrender I had a plan: Use my forced surrender to take control of 3 major Austria armies (total manpower 65,000) and march on Russia while the French try to drive them off of their own land. What I didn't realize was you have to violate neutrality to MOVE the army you borrow. I found this out later but not only did I now have to support 65,000 extra troops but I cant use them. Russia is kind enough to attempt to assault my army multiple times and eventually destroys it. A side effect is my borrowing of Austria's army just decimated it along with about 80,000 russians.
However, during this time my economy comes to a crashing halt. I'm not sure if it was the army I was trying to control or what, but I am now faced with zero income. Without money production in spain halts for many years. France is on the verge of collapse and now Turkey has entered the war against us as well.
The Late Years:
France is now in danger and I don't want to be a part of it. I cancel our alliance and form a simple crossing treaty. My borrowed army has now been destroyed by endless waves of russians. Naples has now levied two full armies and I now have some money. I move on the Papacy and take it. No sooner do I do so than the Russian and Turkish armies (numbering larger than the Grand Army) move into Italy. I am now in deep trouble, considering I control another 40,000 POWs from Russia, which I retreat to sicily. Since England controls the Mediterainian with Nelson's fleet I am forced into a dillema:
France is on the verge of collapse. This is good. They have 800 glory points (game ends at 1000) and I am well into second (650 glory). Third place has only 400. The Spanish Army has regrouped now, having had some months of prosperity. It now consists of 4 fully stocked armies, including a Cavalry-Only army with +50% charge power. My Cavalry will prove to be the hinge for victory, as I will use it like a battering ram to break my opponents into multiple pieces.
So the problem is this. If I do not send my armies across france to rescue Italy I will lose a very valuable position that provides me a lot of glory points every turn (and units every year). If I send my army across to Italy I will be forced to smash through a large number of enemy armies. I am not worred about losing, my force is now much stronger than the enemy armies that are in the way. However, this means the enemy will be forced to divert their attention away from france. If I give france the time to recover they may be able to defend Paris long enough to win the game.
I make my decision: I will save Italy. My armies move swiftly across south france. Total number of over 250,000 plus an additiona 60,000 men in Italy I carve a path through over 200,000 enemy units. Russia, England, and Turkey didn't see it coming and they never mustered more than 80,000 units against my 250,000 in a single battle. My forces Arrive in Naples and lay siege to it. With Naples under my thumb Italy is now safe, barring a sea invasion. However, my worst fears are realized when France counter attacks the combined forces of Austria and Russia (I having wiped out Turkey and Britain from southern europe).
France now has 900 victory points and I still trail by 100. Austria surrenders after losing its army. France wins the game: Final score France 1010 Spain 850. I was in second place since the onset of the game and stayed there. I could never muster enough glory points to topple france. My objective to betray france never got realized. Since I was at war with every country except france, I feared that defeating france would only cause open season on spanish hunting, as all 6 other nations converged on their only enemy, Spain. This forced me to hope the allies could defeat France on their own, but alas, France retreated from Prussia and never attacked Russia: Concentrating on hanging on to whatever they could.
I think eventually the allies would have defeated france. on the final turn Britain had taken Normandy and Britany and the provinces on the west front of Austria all belonged to Russia. With me hanging on to Italy for dear life I never had the opportunity to assault Ireland, Russia, or Constantinople. Prussia would have been my next objective.
Side note to anyone who wants to try Spain: The Papacy is a wonderful objective to capture. I would have done it sooner had I known. The huge culture score of the papacy not only boosts national morale but also supplies at least 1, if not 2, glory every turn. Plus with a little work you can have the Papacy produce armies, meaning you can organize the armies of Naples into real fighting units. Also efficient was my selection to upgrade Cavalry Charge. That plus your commander who gets +30% cavalry turns the Spanish horsemen into a force more dangerous than any other on the field. I had multiple charges inflinct between 3 and 5,000 casualties (half of an entire division).
But so it ends: Spain... hard to play as but I enjoy the challenges.