Styleforum.net has a lot of great information. They tend to focus on very high end, but if you ignore this fact you can still learn a lot there.
Saks Fifth Avenue outlet and Nordstrom Rack have great options for shoes at reasonable prices. Nordstrom itself has two big sales a year, one right now (directly after christmas) and another in the summer. There is also an anniversary sale for card-holders which is better than either. Brooks Brothers has a blowout sale every June which is excellent if you like how they fit; I am a bit slim and they fit me like a fucking bag.
Hugo Boss recommendation is a great one. Their slim fit is very well tailored off the rack. DKNY and CK Steel are also well tailored if you're on the slimmer side; they're a bit lower quality than boss though.
When you buy a dress shirt, here are what the cuts mean:
Regular/Classic - Huge - meant to hide being 30-40+ pounds overweight or just having a very very stout frame
Trim/Sharp/Tailored - Much Slimmer than classic; can still be 15-20 pounds over weight and this will look good
Slim - Tiny bit slimmer than trim. 10-15 pounds over weight still OK here.
Extra Slim - Made for exceptionally skinny folks; 6ft 130 pound types. Honestly I think this cut pushes it a bit.
The above sizes are rough and based on popular brands. Note that for the most part, expensive dress shirts (150-200+ retail) will generally be made in Italy and sort of imply some sort of slim/tailored fit, even though it may not explicitly state so. I have noticed high end English dress shirts, Hickey Freeman etc, are still pretty boxy despite their quality/price. I also consider Brooks Brothers and David Donahue slim fits to fit like shit, so try them on before buying.
For dress shoes, lot of differing opinions here. It's worth noting that cap-toe oxfords are the gold standard super conservative shoe and should be worn in conservative interviews etc.
Cap-Toe Oxford:
Points to note: Lacing; Comes to point at front; Stitching by toes, ie 'Cap-Toe'
Loafer - Much more casual than above shoe. Good for business casual or night out.
Note - Slip on
In terms of dress shirt fit, these are the areas that I think are important to look at when you're at the mirror:
1. Shoulders - the sleeve should ideally begin directly at the point where your shoulder starts to fall. The further past this point you accept the cut to fall, the sloppier you will look.
2. Fabric coming off upper arms - If you pinch this to your arm, this shouldn't really be more than two inches or so on either side of the upper arm.
3. Fabric off mid-waist - Inch and a half to two inches.
4. Fabric by belt - Depending on cut, you will probably have to tuck some excess fabric in the small back so that this looks right. If you have to tuck in too much and the fabric is billowing off your lower back by like 6+ inches, get the fucker tailored or don't buy it. If the upper body fits well and this is fucked up, getting a shirt a.) 'darted' or b.) having the sides taken in will probably accomplish what you're looking for.
5. Sleeve should sit about where this guy has it on 5, at the bottom of the thumb. I'd say his sleeve on the other arm look like it's down too far. If the arms a little too long, use the tighter wrist button so that the sleeve doesn't creep down too far. It's usually better to go a bit longer than shorter on the shirt length if you're an in-betweener. A button can solve the 'little too long' problem, but if you put your elbows up at a table, there's nothing you can do about showing 4 inches of wrist if you go too short.
6. Fabric coming under arm pit - This can drape down maybe 2 - 3 inches at most. If you have too little fabric, you won't have enough flexibility in the arm.
Biggest mistakes I see in shirts fitting are shoulder cut being way off and far too much fabric at 2. and 6. The other problem with 6 is that the lower you allow this to go, the further down the shirt is going to fit correctly through the upper chest. If your shirt doesn't fit across your upper chest correctly, you may look like you have man boobs whereas a well fitting shirt will make you look in shape.
In terms of dress pants, few important things to note:
Pleated Dress Pants - The natural dress pants crease going all the way up to the belt line
Flat Front Dress Pants - Natural crease stops at about mid thigh
If you are going to wear a suit, your dress pants should generally be pleated. Pleated dress pants usually have 'cuffs' by the ankles (rolled up fabric on the outside).
If you are going business casual, people generally wear flat front dress pants. These should generally not be cuffed at the ankles.
Wool is gold standard for pants and suit coats. Polyester dress pants are the common and cheaper variety; they look ok but will pill over time.
Cotton is gold standard for dress shirts. Non-Iron dress cotton shirts are essentially cotton dipped in formaldehyde, wrinkles will generally come out if hung. These shirts also tend to not breath as well and can have a bit of a glean to them. I do not recommend any dress shirts with Polyester, tend to look a bit off. Geoffry Beene Sateen etc looks idiotic and cheap, do not wear it.