It's not a mistake. Just because the numbers are against us means nothing because we are young and have all the time and energy in the world. Thank you for your amazingly helpful comment.
First of all, regadless of my opinion about your project, congratulations for deciding to do something and actually getting it off the ground.
Now, regarding http://theboxngo.com, the first thing I would personally like to see is a clear statement explaining exactly why I should be using this as opposed to eBay, local classified ads.
To answer your question, your marketing strategy should very much depend on the core value you provide which - to me - is not clear at this stage.
I'd say the best way is to be in college and seed it among your friends/connections that have their own circles in college. Ex: residences (perhaps a don who can speak to the freshman on their floor), clubs, classes, etc.