I'm kind of wondering about an OD suit though
Depending on the shade, a lighter olive , khaki, or tan are popular colors for summer weight suits, and I've seen some slimmer guys do well with olive-y looking suits during other months.
Lots of good advice here. Depending on where you live you might also have access to Jos. A. Banks, which is a chain of discount stores with a good range, kind of like Men's Wearhouse. Heck, once you get your size down, try eBay for Brooks Brothers and other high end stuff! You can't go wrong with a basic blue or grey pinstripe, a white button down collar short, and a subdued red tie for starters. A few more shirts(blue, and maybe a thin candy stripe in red and blue) and a blue tie and you can go just about everywhere.
At a lower price point there's always JC Penney, too: they have two house brands, TownCraft and Stafford(the "better" of the two), that offer mix and match suit jackets and pants, which is good if you are truly hard to fit, and a decent line of dress shirts. Penney's has a sale apparently every 32 minutes, so you can really stretch your dollar if you get them at the right time.
There's an important point made here, and one which I ignored for many years: quality costs more because it's often worth it. A better quality suit, made with better materials, just fits better, looks better on you, and usually will wear longer than a Haband $99 deal. Sales people who know their stuff can often make a huge difference, as can a good tailor, but you'll usually only find this sort of expertise in the better stores. It is worth the investment to get at least one really good suit, short, and tie. Same with a good blue blazer and overcoat if you're in the kind of place that has wet and cold weather.
When I started working in the "real" world in 1982, suits and or dress shirts and ties were pretty much universal for certain kinds of work. First we started seeing dress down Fridays, then dress down summers, then IT and support staff going casual full time. Nowadays, outside of Wall Street types and law firms(and of course others), collared shirts and chinos are pretty much standard almost wherever I go, so factor that into your clothing budget down the road.
Also, do yourself a favor and get a *good* pair of shoes, something comfortable but appropriate for a suit. Money spent on shoes is usually worth it as classic, high quality shoes can last 20 years with resoling and regular care and never really go out of style(I'm thinking cap toe oxfords, brogues, lace up shoes). Not a bad investment!
