As Maratha , I conquered all India , Persia and Ottoman Turks.
By the time I step in Europe the Prussians had 1 province and the Austrians were eliminated by the Polish. So Europe had 3 major powers. British, France and Poland.
Russia was having a hard time fighting Sweden who have expanded east.

Maratha was underpowered ,military speaking, BUT i used their military Pros:

1. FULL STACK armies with 5+ star generals.
2. Army composition: Sikh Musk. , Swordsmen ( excellent to outflank the European elite infantry), Great - Organ Guns and Heavy cavarly to surround them (India have good cavarly) and Hillmen as light infantry.
3. Have yours thugs assassinate their multistar generals before you fight them.
4. Sabotage their advanced barracks.
5. Use Afghan/Kurdish Hillmen as light infantry( not jaegers but they do their job well if used wisely)
6. Fight defensive battles mostly.
7. Finally, remember that human intelligence is always superior that any CPU A.I.....!

I crashed the Polish and French (yesterday I took Paris, now the french are starving in low level provinces like Alsait-loraire and Flanders). Now I will fight my way with the British....