I've had a few girls tell me my style is lacking but they haven't told me where to go or what to buy. I have a few business suits but usually I just wear a t-shirt and jeans. What I am looking for are brands where I can get a nice, button up solid color shirt and some slacks sort of thing - I really like Armani but like I said cost is a factor. As far as size goes I am 40" chest 32" waist and 5'9" so fitment isn't a problem wherever I go.
H&M! Love their clothes (for both genders) and their prices are usually pretty cheap, but they still have good quality.
J Crew is good too for classic stuff, which seems to be what you're looking for. (It's a bit on the more expensive side, at least for me, but not outlandish.)
look on ebay, you can get some cheap dress shirts on there brand new. I buy nearly everything I wear off ebay, you can find really unique stuff there, especially if you buy from china, you just have to make sure you get the right size cause their sizes are very small.