Dress me for work ^^

Starting my first professional job after college on January 3rd. I got very lucky and slid into a really good position so I want to make sure I dress properly.

Business casual, not a cold environment (Texas)

One of my primary concerns is making sure I dress "aging-up" not down. Most of my coworkers are 10-30 years older than me and I have a client facing position (account manager at a consulting firm). I don't want them to feel like their account is being handled by the company child. I don't necessarily need to look old, but I need to look like I have myself together.

Typically I'm no slouch for dressing so I just decided I'd head to the department stores and through the mall and pickup what I needed. Turns out, I'm not finding as much as I had hoped. The shoes have rubber soles and the shirts are low quality.

I've got chinos and wool pants from banana republic. http://bananarepublic.gap.com/browse/product.do?cid=34724&vid=1&pid=834541

I'm having trouble finding shoes (with leather soles), nice shirts, and sweaters that work well.

Who makes a great white (and other) dress shirt? I don't wear an undershirt so I'd prefer if my nipples didn't show through some crappy cheap thin fabric. I'm slim, slim fit is a must, and I'm not opposed to tailoring.

Here's me for reference:

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc7/394483_695845090694_199305110_34404021_1978911791_n.jpg I'm 5'9" and 160-165lbs. I typically wear a size small shirt and 31-32/30 pants.

The pictured shirt has been heavily tailored. Chinos are slim from Banana Republic. Shoes are brown leather wingtips, which are a bit too bold I think for every day. I prefer lace ups.

Any cool stuff you want to show me would be great. I need a closet full.