Personally don't think you can go wrong with a pair of classic black or tan oxford's. Tan would mean you could potentially wear them in more smart-casual situations. Depends how formal the workplace is. Mates of mine don't own any smart shoes and wear desert boots/chukka's with a suit for interviews. I woudn't do it, but fair enough on a budget, as they are not going for jobs that will require a suit other than for the interview. In your situation I would invest in something more suit appropriate from a classic shoemaker like loake or similar. I got some nice Charles Trywhitt (made by Loake) tan oxford's a while back from eBay for not very much money at all. They look like they have barely ever been worn. You could go down the eBay route, or pay full whack/look for sales.