I did this last year. VERY and I mean VERY low budget. Screen-Accuracy freaks look away now :lol
So I got a generic brown pinstripe suit off ebay for under £24, dissapointing as it seems no-one selling suits knows how to colour correct their pictures for accurate representation.
Put together with a blue shirt I already had, generic trainers and the new pair of glasses I'd got which were close in style (I needed a new pair and decided they suited me). I also started off with a vaguely-close tie, but I got too warm.
suit (dissapointingly darker than the ebay photos made it look):

trainers:
And me at my archery club (which explains what I'm looking at and the glove on my hand):

.... photoshop magic can add the blue stripes if you want

(though now I'm wondering if I could overpaint them somehow)
Of course, the caveat is, the lower the budget, the lower the accuracy. However... even without waving the sonic around, most people got who I was. So, for a one-shot costume in a rush I was pleased. If I were to do it again I'd spend more time looking for a nicer suit (assuming I don't suddenly win the lottery and can afford a Magnoli or Baron suit)
Long story short: Accuracy = low, cost = low, fun = high.