Dark brown derby is pretty versatile - you can wear it with anything from jeans to chinos to odd trousers ("slacks"), even a suit if you are not English, though I'd prefer an oxford shoe instead. The difference between derby and oxford:
Another thing if you are new: Don't rush into buying things too fast. Read the threads and articles here and elsewhere, get some books (Roetzel's Gentleman, Flusser's dressing the man etc.), but wait a couple of months before you feel confident that you know enough. Your shoes are perfectly serviceable as they are and they should last you long enough before you learn about what makes a good shoe.
Thanks for posting that picture. Can someone advise me if these Sebagos are formal enough to be worn with a suit, when necessary? Although they are plain toe oxfords, there has to be other elements (such as leather vs rubber soles) separating a dress shoe from a casual shoe, right?
I'm not sure about the light (wood?) soles and burnished tip (which I really like). They will mostly be paired with jeans or khakis, but I am looking for a versatile pair of shoes for business school.