These are some steps to winning and other tips.
How to Dominate as Polish
Start amassing an army near Crimea. You will want these ports in the black sea. Get it before Russia can. If Russia gets it first, do not declare war. They can be a valuable ally if you bit of more than you can chew especially with the Ottomans.
Get rid of the Ottoman's control in Europe, then kick out the Prussians. For bonus points, you can go for smaller nations near you. Do not waste much military power on these.
Once you have removed the Ottoman's control in Europe, attack their capital. be sure to have two armies handy, one to guard the capital from rebellion, and the better of the two to continue your crusade. The capital is the most likely to rebel once you capture it, so you must have an army there.
Take out the rest of the Ottoman cities and towns then neighboring nations such as Georgia and Dagestan. Then, since the Ottoman empire connects to India, attack the Persians and then the Mughal empire, or more likely the last city in the Mughal empire. Then, you have the option of attacking the Russians or the Maratha confederacy. Both at one time, with two or more armies. If you do that in time, you should have a victory!
- I have not actually tried this particular strategy, however, I have taken the Ottomans as the Polish. I am about mid-game in that one.
- This may be a burden on you treasury, so trade, trade, trade!