To preface, I apologize for any spelling or grammatical errors
FIT IS KING
Learn what fits for you. I'd highly recommend subscribing to GQ and or Esquire (I do both) you can get em each for $10 for a year if you know where to look. Pay attention to the advertisements as well, they will give you an idea of how to put together an outfit.
Slim fit is a trend. Trends are cyclical. Remember how people dressed 10 and even 5 years ago. So buy expensive skinny clothing at your own discretion. Compare Pierce Brosnan Bond to Daniel Craig Bond.
Pay attention when you watch movies and tv shows to what guys are wearing. Most movies and tv shows made within the last 5-7 yrs have well dressed men with well fitting clothes. (Bond, X-men first class, 500 days of summer, Mad Men, Suits etc.)
Become a member on styleforum. A lot of the members are kind of stuck up and douchey, but they have the best information on how well clothes fit. You can even post photos of yourself in suits and get their opinion on how it fits (just make sure to block out ur face). Styleforum is also a great source for finding out what brands are good quality.
Spend time and start cheap. You will not know what fits you at first. You will sort of know what fits you after doing some research, but believe me, your clothes will only sort of fit. This especially goes for small guys who went through the baggy clothes trend of a decade ago. I have a whole closet of clothes that almost fit, but do not exactly fit. I purchased them during the first year when I was just getting into clothing Well fitted clothing will feel very strange, and likely constricting. So start off by buying cheap brands. Think H&M, Forever21, or Express. They all are pretty slim fitting and stylelish. Forever21 is known to basically rip off of current fashion shows.
Quality is overrated in my opinion, but does have its place.
http://www.styleforum.net/t/140387/the- ... fwhsql/405
This is a great resource on high quality suits. Be careful though, many of these brands are exponentially more expensive than your Armani's and Gucci's. I went through a Neoplolitan Suit phase, and girls didn't know or care that my Kiton's, Brioni's and Isaia's had hand-sewn buttonholes or a hand felled sleevehead. Even free floating canvassing is overrated, but does have its benefits. Make sure your suit is not too shiny, and is made out of wool. Higher quality wool/cashmere/vicuna does not equate to durability, only softness. It does not "look" more expensive.
On designer suits:
I actually find they are worth it, but do not pay full price. You can get Armani Collezioni at off sake for $600. The quality is crap, but the cut and fit is worth it. Girls will notice. Bare in mind, they may go out of style in about a decade.
I wear Turnbull and Asser (the shirts of James Bond yay?) and Finamore Napoli. Nobody gives a shit my shirt retailed for $500. Polyester can last through a nuclear holocaust and doesn't need to be ironed. Here's where it gets tricky. If people can tell the difference (90% of people can't) cotton looks better than polyester. Higher quality cotton feels better, and looks way better after a few washes. My brooks brothers cotton shirts look kind of janky after a few washes.
Never spend a lot of money on jeans. Think of the popular jeans 5 years ago: Diesel, True religion etc with crazy washes and boot cuts. Now it's slim straight legs raw unwashed denim. Buy jeans knowing they will go out of style in 5 yrs. That being said, levi's or gap are pretty good for the money. You can find raw denim there for decent prices, and even some fairly cheap (~$70) selvedge. Levi's 501's are the most classic. They are the original jean, and you don't have to worry about them being too baggy or too hipster skinny.
Polo shirts like Lacoste will not last any longer than something from Jcrew or Gap. You are paying for the little alligator. Period. Figure out what fits and wear it with pride. Don't wear polos with khakis and keep at least 2 buttons unbuttoned.
Big trend currently are henleys, v-ncks and horizontal striped nautical shirts. Love them. Remember though it's a trend. Find what fits, don't over pay, you're not getting much increased quality for nicer t-shirts.
Splurge on shoes. Leather dress shoes. One pair black, one pair brown. Don't buy anything with a square toe or a pointy toe. You want a nice rounded toe. Look at pictures of english brands such as John Lobb, Crockett and Jones. That is the kind of toe you want. Either no design or a cap toe. Some say cap toe is more formal. Keep it simple. Wing tips/Brogueing is fashionable now, but 8 years ago, only your 80yr old grandpa wore them. 8 years from now that may be the case again. Leather quality is important because cheap dress shoes will deteriorate faster. Poor quality leather will crease faster and look shitty. It will also scuff easier. Cheap shoes may be fake leather (ie plastic) and will tear. I believe Aldo is plastic but I have not touched one in a while. Buy Alden not Aldo. Allen Edmonds is a decent entry point. Go for leather soles over rubber soles, they are sleeker and you can replace the soles when they wear out. I enjoy goodyear welting but you are paying an extra $200-$500 for the welt.
60% of what you are paying for is for the label and advertising. 20% of what you are paying for is the design and cut, 20% is quality. These numbers are gross estimates. Avoid anything with garish labels, they will make you look douchey, gay, or like an Asian tourist. The design/cut is only worth it if you are buying a suit, jacket or coat. You can find shirts, jeans etc that fit just as well that are not designer.