Sid, i will give you a couple of options, if i miss anyone i would like someone to correct me:
1º- Tax collectors. By the end of each year, they will give you a lot of cash. The more provinces with Tax collectors, the more gold you will earn per year. They also increase province income by 1 or something like that. Note that it grants a +3% revolt risk in the province where it is built, but it always pays off.
2º- Merchants are good, but i would say they are only good when you get trade tech level 3, because you can get monopolies, which DRASTICALLY grant you a lot of cash, both in short and long terms (short terms, meaning monthly income, long terms, because of yearly income, which are amongst the best ways to raise massive gold reserves in my opinion). Note that it is hard to get trade tech level 3, specially as China.
3º- Building Manus, not only does it boost the specified tech (example, refineries help trade tech), it grants 12 extra income in provinces with the required resources (example, refineries in sugar/wine provinces) and lastly, it grants a 2% growth bonus and a -1% revolt risk to the province in which it is built. To build Manus, you need the specified tech, which, is very hard to get as China.
4º- Trading posts aren't actually that good, unless you have a monopoly on the current CoT, and if the province where the Trading post is built has a "rare resource" granting massive trade to the CoT where you have a monopoly.
5º- Having always a good stability, not only does it reduce revolt risk, it increases gold income if i am not mistaken, and it also increases population growth.
6º- Colonizing/Conquering new provinces. The more provinces, the more tax collectors, the more gold you earn per year, the higher the trade value on your CoT, the more gold you earn per trade. Please, note that building World Spanning Empires also raises your Stab cost, specially if the culture on the provinces isn't the same as your country culture, and also if the religion isn't the same as your country.
7º- Building Mayors/Chief Judges. Mayors reduce inflation per month, increase monthly growth rate on the province where it is built, and gives a +1 province income bonus or something like that. Chief Judges also grants that income bonus but also reduces revolt risk by 1%. Although, to build these, you need a very high infra level, which, as you may know, is hard to get as China.
8º- Lastly, your DP sliders. Maxing out Centralization/Plutocracy/Free subjects grants you extra production/trading incomes. Oh, and the better infrastructure/trade tech level, the more income you earn.
9º- I almost forgot this, but while at peace, get your army/navy maintenance cost in the minimum. You do not need an army with top morale when at peace, even versus rebels, since rebels share your country morale.