1. Pick a suit with a good cut. This topic has a lot to it--I'll do a post on how to pick a suit soon--but for now I'll say get a suit that fits and that has some style to it. I think the majority of people buy and wear suits that are at least a size too big. It's also a matter of finding a good looking suit that doesn't look run-of-the-mill. Stay tuned for more on this another day.
3. Have a good quality, classic pair of dress shoes that you can wear with all your suits. A lot of guys are used to black and would have black as the go-to pair. I'm a big proponent of brown shoes, and I'll wear brown with any color besides black. Whichever color you choose, make them a good pair of shoes that always look good. Good quality shoes will last for years, so don't be afraid to spend a bit extra. You don't have to break the bank to get a pair of lace-ups with leather soles and a classic shape and design, and they'll always look great.
4. Accessorize. I've posted before about tie bars and pocket squares. The simpler the better usually. They give variety to your look without overstating it. You can find a simple tie bar for $25, and a pack of white handkerchiefs for $7 or $8.
6. Watch for sales. I'm always proud of myself when I've picked up nice clothes for half the price or better. This way you can wear nice labels and not feel badly about it. I wore an ensemble the other day that I pieced together over a few weeks. A blazer, trousers, shirt, and shoes. I paid a grand total of around $155 for all of it, normally priced it would've cost about $750. No exaggeration. Places like Banana Republic have sales all the time. You're not up to the minute with fashion perhaps, but being behind by 2 months isn't a bad trade for the savings, and no one will know the difference.