Career advice(student)

I’m a freshmen in college right now and I need some advice. I go to a non target(UCSD) and I plan on networking a lot and joining a few clubs to increase my chances of breaking in. I also plan on transferring to USC or a better school. My major right now is business economics.

In the chance that I don’t break into a BB after I graduate, what can I do? I don’t know much about the field, but this is what I know. Please correct me.

There are the Bulge bracket banks that pay the highest in IB. JP Morgan, Goldman Sachs, BOFA, basically the big names.
They pay the highest?

Then there are elite boutiques which pay higher than the BBs, but are even harder to get into.

Then we have the Middle markets who pay mid tier? Can someone give an example of how much 1st years make and if it’s possible to transfer from a MM to a BB after a year or two?

Finally we have regional boutiques which pay the least. Same question, can you transfer to a BB after a year or two?

Can someone also explain the relationship between getting a finance internship before you graduate and getting a return offer. Do you do the internship the summer after your junior year, do school your senior year, and then you get a return offer? Also, when would you apply for the internship?

Finally, what’s the relationship between getting an MBA and progressing in your finance career? Is it necessary?