Here are some tips is have for WFaS players:
-Posad marksmen are cheap and pack lots of bang for their buck. They aren't exactly "elite", but for anyone starting out they are awesome, and even when you can recruit professional troops they can be a useful addition to your force. To recruit them, get some staff militiamen from a muscovite region and when they level up, upgrade to Posad.
-If you ever see a large group of bandits with prisoners, investigate. I have found that you can sometimes rescue very valuable units from them, even winged hussars and Swedish Reiters!
-Swedish reiters are excellent cavalry, I'd even consider them on par with winged hussars in usefulness. They are also one of the few types of cavalry that I find useful in siege battles.
-organizing your marksmen into rows and using the "fire by my command" order can concentrate your firepower to deadly levels. Just make sure to let the soldiers fire as they please once your infantry engage, otherwise you may forget about them and leave them sitting uselessly
-once you get 50k+ Thaler, MAKE SURE TO INVEST IN A CUSTOM WEAPON FROM THE WEAPON MASTER.
There is one that anyone can use. Horsemen can use the double-barreled pistol or carbine, snipers can use the Turkish or European muskets, and melee users can get a handcrafted melee item which deals huge damage.
-If you plan on rebelling against Muscovy or Sweden, I'd suggest taking Viborg and making it your base of operations. It is isolated from all but the east, meaning that surprise attacks are less common as there is only one route to attack from. You can also recruit Finnish arquebusiers, which aren't bad.