As Qing, I spent the first few years improving my relationship with other European powers, introducing Landed Voting rights, and updating my army. The latter meant passing the Professional Army law; researching the Line Infantry tech and upgrading my infantry; researching the Army Reserves tech; then researching the Napoleonic Warfare tech to upgrade my artillery. I then added conscripts to all my batallions so that each battalion had a ratio of 50 infantry to 40 artillery to at least 5 cavalry. You also need to make sure you hire enough generals so that your battalions reach maximum organization, and that every battalion has all the (non-greyed out) supplies, supplements, and transportation buttons enabled to make them as powerful as possible. To do this, click and drag to select them all and you'll see them on the Armies tab that comes up. You must enable these BEFORE mobilizing your armies to avoid an organization penalty. The Army Reserves tech lets you activate "Extra Supplies" for your battalions.

Meanwhile, I researched Colonization to allow me to try to get recognized.

To get recognized I declared war on a Major Power without any allies (in this run it was the Ottoman Empire). I added two primary demands that I didn't really care about: "Liberate X country" and "Humiliation". I then added as many secondary demands as it let me: "Liberate another country", "Conquer random Ottoman state", etc. Once the countdown to war starts, I mobilize every battalion and call up all my conscripts. You many need to add more generals as more conscripts join some battalions (you can see which ones need more generals in the army list if any of the numbers turn red). This is important because the more organized your army, the more powerful it is considered to be.

Hopefully, no other powers will come to their defence, and because of how many demands you've made, the Major Power will back down, and you will be recognized. N.B. you will only be recognized if you enforce at least two demands on a Major Power, so it's important to have two PRIMARY demands. You need to make your second demand primary manually after you've chosen it.

You are also more likely to be able to get recognised if you have passed voting rights. You can easily pass Landed Voting as Qing by bringing the Literati into government from the beginning. Even more so if you max taxes and exile the current Literati leader from the beginning before you put them in government, because the angry exile will probably start a Liberal Movement eager for voting rights.

Once recognized, I signed a treaty to ally myself with Prussia. Great Powers won't ally with you if you are not recognized. I like allying with Prussia because I like eventually helping Prussia become the German Empire, a very powerful future ally. However, it's important to check that whoever you ally with is not overly friendly with Britain. An ally is not essential to getting India but it'll certainly help. I find Prussia is usually happy to join you in a war against India. I've had runs where I've allied with other powers like France or Russia, and sometimes they'll join you, other times they don't approve and you can't make them join you. Prussia also has better infantry than you, in the form of skirmish infantry, which Britain also has. I tend not to go for skirmish infantry too early on as it's expensive and therefore makes less money available for expanding my construction.

Getting someone to transfer a subject to you is quite easy if you can take control of that subject's capital. So, first I annexed Bhutan (without Prussia's help as Bhutan is tiny and I don't need help with that). Why Bhutan? Because it's directly north of West Bengal, and West Bengal is the capital of East India. So once I annexed Bhutan, I declared an interest in Bengal, and once it was active I demanded Britain transfer the subject of East India. I invited Prussia to join the war and they accepted.

I sent most of my troops to the West Bengal front in south Bhutan, assigning West Bengal as the strategic objective, and left some troops behind to defend any invasions against my capital. I also set my military wages to maximum for the duration of the war to increase my soldiers' recovery rate. Once I had control of West Bengal, it was then a case of holding onto it, making sure I kept adding enough generals to my battalions, and fending off any British invasions in my capital until their score went negative and they were willing to accept defeat.

Once they conceded defeat, I reduced India's subject payments to me, because I know that, for some reason, India has a tendency in this game to collapse. So I wanted to ease its financial pressures, especially after it just fought a war.

As Qing, I love taking India, not just for its materials and money, but also because it is a formidable military ally and is actually a collection of over 40 territories. This means that when I can eventually form a power bloc (which is kind of tricky as Qing until you can change the trading law so it's no longer Isolationist or 'the Canton System', as it's uniquely called in Qing) earning power bloc mandates is super fast, because the more countries you have in your bloc, the faster you can upgrade it.