Sweden

[Zarky]

Taking the remaining provinces in eastern Russia is unwise unless you have obsession with dragoons or +6 to lower classes happiness from ministers since they are slowly developing regions with no way of fighting unrest expects waiting it out and removing taxes, my personal suggestion is that after you get Karelia, Archangelsk, Muscovy and Ukraine you get peace with them by offering them roughly 5000 and some tech for trade rights and peace, works every time and when they are that weak they won't backstab you so long you keep decent garrison, which is must in Moscow anyways.

Once properly developed Moscow can rather easily hold 2 schools in the later stages of the game where you have lots of clamour to reform, Archangelsk and Karelia are useful to capture since they have 3 fur traders put together (2 averages and 1 low yield if I don't remember wrong, ones in Finland and Sweden are also average).

My personal strategy which I find effective is to deal with Denmark ASAP, and yes, that means taking Iceland. I send some 4-6 line infantry there and then later use same forces to capture myself Pirate islands from American theater.

Once you own Denmark, Hannover will declare war on you but if you have trade agreements with its allies, they shouldn't be able to drag major powers into war with you, they are easily dealt with by keeping garrison of 4-6 line infantry (cavalry or artillery not essential) in southern Denmark.
My plan is to form "Baltic Ring" which means owning every single region that has connection to Baltic Sea, including victory condition region Berlin. Baltic Ring is important since creating it protects most of your core territories from unlikely but very real naval assaults. All you need to do is keep mediocre fleet between Norway and Denmark.

In 1.5 Prussia often loses East Prussia after some 10-15 turns if not earlier, you need to be ready to capitalize on that by taking out Courland right after Poland-Lithuania captures East Prussia and then move to East Prussia and claim it as your own, this also removes most resistance to foreign occupation which is good since the region is almost filthy rich after you destroy the entertainment building in there and build another industrial building instead.

You are safe to send Indiamen to trade theaters if you wish but I strongly suggest taking out Denmark before sending any out of your ports. You need to be more careful if Crimean Khanate is destroyed, which has happened in every single one of my games, but before you start massing a gigantic trade fleet, keep upgrading you fur traders for a less risky way to make more money and destroy pirates in American theater, then you can convert those 2 shipyards into ports and you have 2 regions with ports producing sugar and they are within one turns reach from Brazil.

This is long bit I've written and I'll continue this later if needed.