Jaunpur into Delhi.
1.) Give land to the Jains. Get their influence up to 75 with interactions. Get 150 diplo points and accept both cultures, Bihari and Hindavi.
2.) Activate the mission for permanent claims on Delhi.
3.) Rival Delhi
4.) Unpause the game.
5.) Ally Multan
6.) Declare war on Delhi on 11th Dec 1444 AD. Call in Multan for promise of land (which you won't give them)
7.) Full annex Delhi and acquire Sirhind and Jangladesh as subjects.
8.) Core only the province of Delhi and then tag switch to Delhi
9.) If it is pre 1450 AD, the Sirhind independence event can fire, unless you are at war. So keep warring with nations with your cores, like Kashmir is an easy prey and then Malwa's subject Kalpi and then Multan after the truce ends from broken alliance due to low trust.
Enjoy owning the entire Gangetic plain from Kashmir in the North West to Bihar in the South East by 1470 AD, having the highest development in the world second to Ming.
First three Idea Groups: Humanist, Diplomatic, Quality(or)Trade.
Improve Relations Stacking Modifiers: Humanist (30%) + Diplomatic (25%) + Humanist-Diplomatic Policy (20%) = +75% !!!
If you feel your military needs some help, take Quality (cause Delhi usually has bad military ideas) = Quality-Humanist Policy (gives Prestige and reduces Prestige Decay great for boosting Improve Relations), Quality-Diplomatic (gives +1 Diplo Relations and -0.5 War Exhaustion)
If you feel no other Indian nation can oppose your military, take Trade: Trade boosts income considerably, but more importantly gives more Merchants who can use Improve Relations trading policy.
With this setup you can expand fast as mentioned above and continue that pace. Basically become super aggressive. Needless to say first Age of Exploration ability should be Reduced AE.
P.S. With this technique you can quite easily own all of India north of the Narmada river before 1500 AD, without breaking a sweat.