Ok, ill go with something brief for now...
In general, my advice is to do nothing and relax. There will be lots of other people in the same boat as you anyway, and you'll be fine. Admittedly, this is more likely the case at the GSB than at other schools (were, for instance, those with a CFA Level III cert will self select out of basic investments, while at other schools you may well find those people in your class), but in general, I don't think its something you have to do. Enjoy your free time now because time gets to be pretty precious later.
As for what to study, I'd say there are four general areas that are probably considered rudimentary.
1: Statistics:Pretty fundamental, especially important if you plan on doing finance. I prepared with these notes and found them quite helpful:
https://faculty.chicagogsb.edu/alan.best ... index.htmlIf you want an EASY book to read, I recommend the cartoon guide to statistics. I know, it sounds retarded, and it sort of it sometimes, but its actually something you can tolerate reading.
https://www.amazon.com/Cartoon-Guide-Sta ... 0062731025
OCW Link: https://ocw.mit.edu/OcwWeb/Mathematics/1 ... /index.htm
2: AccountingPainful. Just painful. Not an easy subject to learn on your own. Scribd and many many many other sites have tons and tons of stuff to get you started.
See for instance:
https://www.scribd.com/doc/2541346/Financial-AccountingAlso helpful:
https://ac.boisestate.edu/ac205novakes/More complete, despite the stab-me-in-the-eye color scheme:
https://intra.som.umass.edu/mannino/Cove ... %20630.htmI've also attached some notes I had found somewhere once. Not very helpful if you havent seen accounting before, but still.
OCW Link:
https://ocw.mit.edu/OcwWeb/Sloan-School- ... /index.htm3: EconomicsPersonally, I'd focus elsewhere but.... if you need a memory jog:
https://web.mit.edu/~bilalw/www/cases/microeconomics.ppt(yes, its a GSB ppt hosted by someone at mit, cute)
If you want something more substantial:
https://ocw.mit.edu/OcwWeb/Economics/14- ... /index.htm4: Investments / Basic FinanceProbably not worth studying if you have seen this stuff before. Invest in an HP 12C calculator now and learn it over the summer. I recommend the anniversary edition.
OCW:
https://ocw.mit.edu/OcwWeb/Sloan-School- ... /index.htm