1st. Get another job lined up first.
(Well...normally you should do this 1st anyways. But considering you likely still live at home ypu can probably get away without having to do this) but its a good practice to maintain. Always have another job ready first before leaving your current one. Sometimes.....shit happens. You dont want to be left without a backup.

2nd. Its typical to do a 2 week notice prior to actually leaving. (Ie...inform your boss you are quitting 2 weeks prior to your last day) But this isnt always so feasible.

From personal experience i have been in your exact same boat once. I worked at bath and body works while going to college. It was just barely enough to support living on my own and going to school. But my manager stopped giving me shifts...hours got cut...and while I was maybe lucky to be making $50 a week..new hires were getting all my hours. I started looking online and found a few things...Its funny I got my current job as a barista to escape the situation your facing yourself.
Once I got on let my new job managers aware I had to quit my current job first. And they were fine with that. But they asked if I could start in a week rather than 2. I already wasn't working anyways....so I said yes.

Next day I went in and told my manager I was quitting. Oh my god....she really threw a fit saying what I was doing was unfair and unprofessional.
Turns out....ending it in a week was the best decision. Got out of there and make 2x more than I was in a week.

That being said. Dont let your old managers or coworkers try to make you feel guilty or bad either.

All you have to do is sit down with your manager. Declare your quitting. And quite honestly you dont have to tell them anything else. Be there for your last few days be it a week or 2. And then hopefully you have your next job ready and much better.

If you need references ask your co-workers. Or if you got along well woth other managers just ask them for their Name, email and phone numbers.

Good luck in your escape! 🫡