1) The ideal is to have a suit wardrobe such that you only wear the suit once every week. Wearing them more frequently than that will make them wear out faster than they should. (If you want to go to aspirational levels, one can say that the best would be to wear a suit only once a week, and to have separate sets of suits for spring/summer and winter/fall.) For someone who wears a suit every day, this generally works out to six suits (five for workdays, plus one spare/to cover things on the weekend).
2) Your best bet for reasonable price may actually be ebay. Run a search in your size based on well-made brands, such as Samuelsohn, Oxxford, Southwick, and Ralph Lauren. You can even set the search up as an RSS feed.
2a) Barring that, there are lots of places to look for some good suits. Locally (I assume you're in Chicago from your handle) Brooks Brothers, Nordstrom, and Neiman Marcus come to mind as places to buy a good suit. Online, you can expand to J. Press and O'Connell's. Jos. A. Bank can be a good price, but 1) their suits have very boxy shoulders that may not flatter or appeal to you and 2) only buy from one of their "Signature" or the "Joseph" lines; the lower-tier stuff is not great. The made-to-measure suggestion lower in the thread is a great one: that's often the best value if you can make the initial investment (which might not be more than regular price at some of the above). If you want to be a bit indulgent, the Chicago Paul Stuart is lots of fun.
2b) More important than going to one particular place is getting a good, well-fitting suit. Look for something that's fully or at least half-canvassed, with a "super" number no higher than 120s (a lot of suits are made now with thread counts as high as 150s, but the thread is thinner, weaker, and less durable). Make sure it fits through the shoulders and doesn't pull or gap in the front. Get your pants cuffed with "slight break." Finally, watch out for "fashionable" suits: a lot of stuff on the rack right now is actually cut too short for the tagged size. You'll look very "with it" right now, but a wool suit should last a long time, and the my-suit-is-too-short look probably won't.
2c) Last thing: make good color choices. Navy, charcoal, medium gray, then some stripes, windowpanes, and glenn plaids. Don't buy a black suit unless you're going to a lot of funerals or your new job is "undertaker."