I will give you an overview of each civ:
Portuguese:
Meat Eco is really good, while gold eco should be moderate. Each age, they get a new Town Center. To use this civilization appropriately, you must constantly build settlers so you might need the "Medicine Shipment." Note: you need the Unique Church shipment for the meat gathering.
They get two Factories and get a good navy too, meaning they are good at fishing also. They also get the strongest walls.
Their military is very strong. For example, their musketeer is rivaled with the Redcoat for power. They also get an awesome Light Infantry called the Cassadore. Its ranged resistance is huge and can pack a punch to an enemy, but its hp is very low. They also get halberdiers also but you probably are not going to use them as much. They get Hussars and the best Dragoon, the Jinete. Instead of a falconet, they get organ guns which are somewhat better but have less hp.
Military Setup: Most common is (Dragoon, Cassadore/Musketeer, and Organ Gun w/ Mortars in back)
Dutch:
This civ is hard to use in the beginning. Settlers cost gold so you do not have to worry about losing meat. Most of the meat you use is spent on Banks. You can have up to 8 of them (Vanilla) and 10 in (TAD). They only have 54 settlers max so manage your eco well. Make sure to get the Unique Church Shipment and the Bank cards as well w/ factories or else your eco will not be functional at its peak. Placing your settlers: most people usually put all settlers on mills. Its your decision to distribute your settlers depending on what resources you want most. I recommend only using the Dutch near the ocean. With 50 extra pop space, you can use it to fish on whales. Also the infinite Privateer card comes in handy on water maps because their is no build limit for them. I lost to my brother one time because he had 50 of them in Ceylon.
Out of all the nations, the Dutch have the largest military of 150 pop. Their best units are their Halberdier, Skirmisher, and Ruyter. However being a gold using economy, you can afford to spend it on cannons. They can have up to 30 falconets max. Most people don't like this because it leaves them open to cavalry and could lag the game. Their Halberdiers are the best in the game and cause an opponent to feel great stress to fight them in large numbers. However it is not recommended to spam these because they train slower. You can also make them faster as well. Ruyters are the "Dragoon" for the Dutch, and cost only 1 pop. They are really spammable, but do not put them against Musketeers, you will be sorry.
Military Setup: Skirmisher, Ruyter, Cannons, Halberdiers (if necessary)
Spain:
Sadly Spain does not have one of the stronger ecos but its military is quite powerful. With having only two factories and a slow eco, its military causes its eco great stress if you spam too many units. Its eco above all is average but its military is above average. It is basically a meat dependent eco like the Portuguese, but because of the exp bonus it is mainly used for Fast Fortress strategies and rushing.In TAD they have the unit called the Missionary which increase your attack of your units by 50% if they are nearby.
The Spanish have many unique units at their disposal. For one they have the only Imperial Pikeman. Most people dont recommend using it because of its wood use and wood is scarce late game, but it is a good cav killer. It can also train fast with the Archaic Schools card. Next is the Rodelero, these guys are basically one of the best spammable units out there. These guys can get rid of Hussars easy. They also get Musketeers and Skirmishers.
The Spanish get 3 types of Cavalry; Hussars, Dragoons, and Lancers. Lancers are one of the best cavalry in the game. If upgraded right, it can do x4 against infantry and basically kill most infantry in 1-2 hits. With the Missionary bonus you can slay anything.
Russians:
This is the only other civ besides the Spanish that gets 1 factory in vanilla and get 2 in TAD They have a really good eco for one and a moderate army to boot. They are a meat dependent economy and a gold dependent economy, depending on what you are doing. They also can make their Musketeers build forts which is pretty cool.
The Russians have the fastest spawning infantry in the game in vanilla. However because of this, their infantry are slightly weaker than the normal. Their infantry also train in batches so they train even faster. They also get a card to increase their siege by 50%. The Russians get a light infantry unit called the Strelet. It is the CHEAPEST unit in the game only costing 37 meat and 10 wood. These guys are the most spammed in early games, later will be musketeers or halberdiers. Strelets are handy when it comes to slow heavy infantry like Halberdiers, so they can be a perfect counter to the Dutch in a way. They get grenadiers too called Parlovs, however it is not recommended to use them often.
Russians have 3 cav units, the Cossack, the Oprichnik, and the Tartar Loyalist. The Cossack is basically a 1 pop Hussar. Do not say they suck, they actually do more damage if you had two of them together. The Oprichnik is the best raider in the game. With siege attack over 160, they can go into a town with ease and get any of the settlers with its x3 bonus against them. Another good thing about them is that they have x3 against siege units too. So they can kill units like grenadiers and cannons without a sweat. The Tartar Loyalist is basically a Royal Guard cavalry archer. But remember that cavalry archers shoot 2x faster than gunpowder cavalry.
Against the French, the best civs would be the Portuguese and the Dutch. The Portuguese have the Jinete and the Musketeer to counter Gendarme Cuiraissers while the Dutch have a huge army and a lot of Ruyters and Halberdiers. But look out, most French turtle and make you waste your resources try to get in their base. So make sure to build mortars and protect them well.
Sorry if I wrote too much...I hope this helps.
[This message has been edited by Rienfleche (edited 08-09-2011 @ 00:22 AM).]