I can't even get a back office job. I don't know what to do anymore.

Long story short, I don't know what else to do. I'm at a disadvantage because I didn't go to a target university, but thought I wouldn't have a problem getting a job. I graduated in 2018, started my own business at the age of 15, worked for a financial services company and sold financial products during college, got a job for a year in the marketing department for a financial services firm (which I loved), and was to start another role in March. The role got rescinded due to COVID-19, and I've been applying to entry-level roles within the marketing and communications departments at banks. The worst part is the main industry I am passionate about is wiped out due to COVID, and my background is very niche. 

I've sent hundreds of LinkedIn Requests and 200+ messages to recruiters. 

I've applied to more than 300 roles, many of which are back office.

I've spent hundreds on resume reviews, financial modeling courses just because I thought it might help and I find it fun and interesting to do and improve my chances.

I'm getting rejected from Client Associate roles and roles that don't even require a college degree.

I've reached out to my very few connections I have who are VP's, and they are too busy to help and aren't that great at letting me know how I can improve since they were poached from other firms and haven't edited a resume in years.

I genuinely don't know what to do anymore. People don't respond to LinkedIn messages, and I'm two months away from giving up my apartment in NYC and moving back in with my parents where there are very little job opportunities. 

Does anyone have any tips or trips on how to really connect with others? LinkedIn no longer works for me, my connections at banks are all in IB (a department which I'm not very interested in and doubt will be able to break into) and are only analysts, and I'm at the point where I will stand outside of the main entrance of a financial institution to just hand people my resume. 

I'm not looking for sympathy, I'm looking for suggestions on how I can do everything I possibly can to at least secure the first interview. Does anybody have any tips?