Any sort of tank that you can get for free on Craigslist (I see everything betta bowls to 10G for free on my local CL in any given week, occasionally a stained 55 but that's out of the question for a dorm room)
Small sponge filter - ~3-9 on Amazon
Small air pump - Probably free with the tank you picked up but lets say $10
Handful of dirt from around campus - Free
Sand from a playground or something - Free
As long as it's not near a window and your dorm is heated you can do without a heater and keep coldwater species, which is the only real impactful recurring energy cost.
Hopefully you'll learn more about being a broke college student in college, frankly that's about all I took away from it, but hopefully you'll have a better time than I did.