gotta learn modern standard hindi with a good helping of urdu slang for the communication with north indians and understanding of most modern hindu literature.
absolutely gotta learn classical and epic sanskrit for the devotional literature and esoteric knowledge. might learn vedic sanskrit one day, but right now that old stuff doesnt interest me. its cool for the PIE understanding though.
gotta learn middle and to a lesser extent modern tamil, middle for the devotional literature, modern for the communication with very south indians.
i also wanna learn telugu, which enjoyed a cultural prestige in the south during its early modern phase, and is still the most spoken dravidian language. im super interested in the apparent euphonicism and in understanding Carnatic south indian music, which is written in telugu or sanskrit apparently. I also like how if I did this hindi, telugu and tamil would form a continuous landmass of my understanding.
lastly, I'd like to learn modern bengali because its another indo-aryan language with many speakers, and using my knowledge of it I could talk to my step brothers wife's family. it would also be neat to speak to indians, pakistanis (with my hindustani) AND bengalis.
as a bonus, and this is a reach, kashmiri. not because its the language of kashmiri shaivism, but because its the language of modern kashmiri shaivis and also kashmiri muslims. maybe I can solve the rift who knows. :P