What should I be doing to prepare for next year's New Grad hiring season

Question is basically the title, but here is more info about me.

CS/Economics major at a large reputable university (not a top CS school as far as I know)

Graduating in December 2020

Accepted a summer 2020 sde intern offer at Amazon (I have no other internships or cs related work experience)

Next semester I'll only be taking 8 credits (2 classes) so I'll have lots a free time, and I want to know the most effective way to spend that time so new grad recruiting isn't completely miserable. I'm mainly interested in working for large companies like Google and MS, and trading firms (Jane Street, 2sig, Citadel, etc).

Should I just be leetcoding from now until applications open next year? I have a few personal project ideas I want to build, one of which I think has the possibility to make some money (or maybe become an actual business, who knows), and would be good to put on my resume. Or should I try to find a part-time cs job in the spring? Obviously, I'll be trying to get a full-time return offer at Amazon during the internship as well, but what should be the game plan starting now?