A black peacoat for guys is pretty snappy looking. I think also having a couple nice sweaters, a nice jacket, watch, and pair of shoes is good for a guys' wardrobe. My school posted this and I agree with all their tips and perspectives on guy fashion:
Oh goodness. Don't dress like a metrosexual. The most important thing is to have the correct balance between looking like you tried TOO hard (aka metrosexual), and looking like you didn't try at all. You want to be casually good-looking, and also make sure your clothes fit your personal body type correctly instead of just following trends.
Here are some photographic examples of some guys I'd say are dressed effortlessly good:
If you want more photographic examples feel free to ask. Basically, if you want to be less country that's fine, though I personally think a casual backwoods style is pretty dang hot, but I certainly wouldn't suggest going to the opposite end and dressing "flashy" and "fashionable". I suggest wearing basic clothes that fit you right. Nothing too baggy, nothing tight either, just a nice, relaxed fit.
LA is super easy, throw flip flops, jeans and a Abercrombie shirt on... And you're good to go. Now NYC is more elegant and depends on the season. Never been to south beach though but I guess similar to LA I'd assume.
I don't know why you would want to but here's a list of what's popular in NYC (esp amongst hipsters :/) Oxfords Printed button up Solid color cardigan Flannel Nice fitting chinos Skinny jeans that you can cuff Boots Leather jacket Printed tops (floral print if you're feeling bold)