doesn't really matter which faction you play or what difficulty level, here's how it goes:
1) make sure you have at least 4 schools in your starting provinces, make an alliance with a big faction and form 2-3 trading agreements with major factions
2) build a full army, put it on ships and sail to india. you can even abandon your starting provinces except maybe your capitol which is usually an income-rich province.
3) land on the southern tip, conquer the province. It will be undefended.
Congrats, your income has just doubled (at least).
4) build a couple of religion towns, gather up your army and conquer the rest of the marathas (who should pose no challenge whatsoever even for your 1 army, so long as you keep recruiting from carnaria (or however u spell it).
5) at this point mysore will declare war on you. if not, declare mysore and take it for yourself.
Congrats, your income has just doubled again :>
6) at this point you should have 6-8 schools running and a ton of gentlemen. keep one of them upgraded, fill it with gentlemen and make a rush for the only real tech that matters in E:TW, rank-fire drill while the rest still out-tech all other factions by a marigin of (i)
7) with your new insane income, either continue conquering india (this would be the long haul), or make some treaty with the mughals and use your new insane income in europe, conquering everything you need to win with your vastly superior armies.
voila :>
TIP: if you start with the marathas, the game will be won in 15-30 turns. depending on how fast you want to win, really.