It greatly depends on your budget, authenticity, and how fast you need it. If you want to get a top of the line uniform it will cost you a bit more up front but buying better quality stuff the first time will save you in the long run. The top of the line stuff is custom made for you so the usual wait time is a few months. I get all my clothing from Wambaugh and White. Ben Tart is also a fine choice as mentioned above. Beauregard's Tailor and The Honest Sutler also make some really nice stuff. I'm not familiar with Yankee Dave's recommendation but I'm sure he'd give you a good one. If you need something quickly or on a budget my go to for the big sutlers is Regimental Quartermaster. C&C, S&S, Fall Creek, and Blockade Runner are all decent. The most important thing before you spend alot of money is do your homework and represent the company you are portraying the best you can and talk to the veterans in your group to make sure you're getting the right stuff.